Merge branch '4273-slash-commands' into 'master'test-8-11-stable-2

Support slash commands in issues / MR description & comments

See merge request !5021

56 files changed, 2613 insertions, 136 deletions

diff --git a/CHANGELOG b/CHANGELOG
index f38057793fb..21737738558 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -72,6 +72,7 @@ v 8.11.0 (unreleased)
   - Optimize checking if a user has read access to a list of issues !5370
   - Store all DB secrets in secrets.yml, under descriptive names !5274
   - Fix syntax highlighting in file editor
+  - Support slash commands in issue and merge request descriptions as well as comments. !5021
   - Nokogiri's various parsing methods are now instrumented
   - Add archived badge to project list !5798
   - Add simple identifier to public SSH keys (muteor)
diff --git a/Gemfile b/Gemfile
index 5d02a147cff..68547b6fac8 100644
--- a/Gemfile
+++ b/Gemfile
@@ -209,7 +209,8 @@ gem 'mousetrap-rails', '~> 1.4.6'
 # Detect and convert string character encoding
 gem 'charlock_holmes', '~> 0.7.3'
 
-# Parse duration
+# Parse time & duration
+gem 'chronic', '~> 0.10.2'
 gem 'chronic_duration', '~> 0.10.6'
 
 gem 'sass-rails', '~> 5.0.0'
diff --git a/Gemfile.lock b/Gemfile.lock
index 03616c377fa..5511d718938 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -128,6 +128,7 @@ GEM
       mime-types (>= 1.16)
     cause (0.1)
     charlock_holmes (0.7.3)
+    chronic (0.10.2)
     chronic_duration (0.10.6)
       numerizer (~> 0.1.1)
     chunky_png (1.3.5)
@@ -824,6 +825,7 @@ DEPENDENCIES
   capybara-screenshot (~> 1.0.0)
   carrierwave (~> 0.10.0)
   charlock_holmes (~> 0.7.3)
+  chronic (~> 0.10.2)
   chronic_duration (~> 0.10.6)
   coffee-rails (~> 4.1.0)
   connection_pool (~> 2.0)
diff --git a/app/assets/javascripts/gfm_auto_complete.js b/app/assets/javascripts/gfm_auto_complete.js.es6
index 2e5b15f4b77..3dca06d36b1 100644
--- a/app/assets/javascripts/gfm_auto_complete.js
+++ b/app/assets/javascripts/gfm_auto_complete.js.es6
@@ -223,7 +223,7 @@
           }
         }
       });
-      return this.input.atwho({
+      this.input.atwho({
         at: '~',
         alias: 'labels',
         searchKey: 'search',
@@ -249,6 +249,68 @@
           }
         }
       });
+      // We don't instantiate the slash commands autocomplete for note and issue/MR edit forms
+      this.input.filter('[data-supports-slash-commands="true"]').atwho({
+        at: '/',
+        alias: 'commands',
+        searchKey: 'search',
+        displayTpl: function(value) {
+          var tpl = '<li>/${name}';
+          if (value.aliases.length > 0) {
+            tpl += ' <small>(or /<%- aliases.join(", /") %>)</small>';
+          }
+          if (value.params.length > 0) {
+            tpl += ' <small><%- params.join(" ") %></small>';
+          }
+          if (value.description !== '') {
+            tpl += '<small class="description"><i><%- description %></i></small>';
+          }
+          tpl += '</li>';
+          return _.template(tpl)(value);
+        },
+        insertTpl: function(value) {
+          var tpl = "/${name} ";
+          var reference_prefix = null;
+          if (value.params.length > 0) {
+            reference_prefix = value.params[0][0];
+            if (/^[@%~]/.test(reference_prefix)) {
+              tpl += '<%- reference_prefix %>';
+            }
+          }
+          return _.template(tpl)({ reference_prefix: reference_prefix });
+        },
+        suffix: '',
+        callbacks: {
+          sorter: this.DefaultOptions.sorter,
+          filter: this.DefaultOptions.filter,
+          beforeInsert: this.DefaultOptions.beforeInsert,
+          beforeSave: function(commands) {
+            return $.map(commands, function(c) {
+              var search = c.name;
+              if (c.aliases.length > 0) {
+                search = search + " " + c.aliases.join(" ");
+              }
+              return {
+                name: c.name,
+                aliases: c.aliases,
+                params: c.params,
+                description: c.description,
+                search: search
+              };
+            });
+          },
+          matcher: function(flag, subtext, should_startWithSpace, acceptSpaceBar) {
+            var regexp = /(?:^|\n)\/([A-Za-z_]*)$/gi
+            var match = regexp.exec(subtext);
+            if (match) {
+              return match[1];
+            } else {
+              return null;
+            }
+          }
+        }
+      });
+      return;
     },
     destroyAtWho: function() {
       return this.input.atwho('destroy');
@@ -265,6 +327,7 @@
       this.input.atwho('load', 'mergerequests', data.mergerequests);
       this.input.atwho('load', ':', data.emojis);
       this.input.atwho('load', '~', data.labels);
+      this.input.atwho('load', '/', data.commands);
       return $(':focus').trigger('keyup');
     }
   };
diff --git a/app/assets/javascripts/notes.js b/app/assets/javascripts/notes.js
index 9ece474d994..2484a07f363 100644
--- a/app/assets/javascripts/notes.js
+++ b/app/assets/javascripts/notes.js
@@ -201,7 +201,7 @@
     Increase @pollingInterval up to 120 seconds on every function call,
     if `shouldReset` has a truthy value, 'null' or 'undefined' the variable
     will reset to @basePollingInterval.
-    
+
     Note: this function is used to gradually increase the polling interval
     if there aren't new notes coming from the server
      */
@@ -223,7 +223,7 @@
 
     /*
     Render note in main comments area.
-    
+
     Note: for rendering inline notes use renderDiscussionNote
      */
 
@@ -231,7 +231,13 @@
       var $notesList, votesBlock;
       if (!note.valid) {
         if (note.award) {
-          new Flash('You have already awarded this emoji!', 'alert');
+          new Flash('You have already awarded this emoji!', 'alert', this.parentTimeline);
+        }
+        else {
+          if (note.errors.commands_only) {
+            new Flash(note.errors.commands_only, 'notice', this.parentTimeline);
+            this.refresh();
+          }
         }
         return;
       }
@@ -245,6 +251,7 @@
         $notesList.append(note.html).syntaxHighlight();
         gl.utils.localTimeAgo($notesList.find("#note_" + note.id + " .js-timeago"), false);
         this.initTaskList();
+        this.refresh();
         return this.updateNotesCount(1);
       }
     };
@@ -265,7 +272,7 @@
 
     /*
     Render note in discussion area.
-    
+
     Note: for rendering inline notes use renderDiscussionNote
      */
 
@@ -304,7 +311,7 @@
 
     /*
     Called in response the main target form has been successfully submitted.
-    
+
     Removes any errors.
     Resets text and preview.
     Resets buttons.
@@ -329,7 +336,7 @@
 
     /*
     Shows the main form and does some setup on it.
-    
+
     Sets some hidden fields in the form.
      */
 
@@ -349,7 +356,7 @@
 
     /*
     General note form setup.
-    
+
     deactivates the submit button when text is empty
     hides the preview button when text is empty
     setup GFM auto complete
@@ -366,7 +373,7 @@
 
     /*
     Called in response to the new note form being submitted
-    
+
     Adds new note to list.
      */
 
@@ -381,7 +388,7 @@
 
     /*
     Called in response to the new note form being submitted
-    
+
     Adds new note to list.
      */
 
@@ -393,7 +400,7 @@
 
     /*
     Called in response to the edit note form being submitted
-    
+
     Updates the current note field.
      */
 
@@ -410,7 +417,7 @@
 
     /*
     Called in response to clicking the edit note link
-    
+
     Replaces the note text with the note edit form
     Adds a data attribute to the form with the original content of the note for cancellations
      */
@@ -450,7 +457,7 @@
 
     /*
     Called in response to clicking the edit note link
-    
+
     Hides edit form and restores the original note text to the editor textarea.
      */
 
@@ -472,7 +479,7 @@
 
     /*
     Called in response to deleting a note of any kind.
-    
+
     Removes the actual note from view.
     Removes the whole discussion if the last note is being removed.
      */
@@ -498,7 +505,7 @@
 
     /*
     Called in response to clicking the delete attachment link
-    
+
     Removes the attachment wrapper view, including image tag if it exists
     Resets the note editing form
      */
@@ -515,7 +522,7 @@
 
     /*
     Called when clicking on the "reply" button for a diff line.
-    
+
     Shows the note form below the notes.
      */
 
@@ -531,9 +538,9 @@
 
     /*
     Shows the diff or discussion form and does some setup on it.
-    
+
     Sets some hidden fields in the form.
-    
+
     Note: dataHolder must have the "discussionId", "lineCode", "noteableType"
     and "noteableId" data attributes set.
      */
@@ -557,7 +564,7 @@
 
     /*
     Called when clicking on the "add a comment" button on the side of a diff line.
-    
+
     Inserts a temporary row for the form below the line.
     Sets up the form and shows it.
      */
@@ -605,7 +612,7 @@
 
     /*
     Called in response to "cancel" on a diff note form.
-    
+
     Shows the reply button again.
     Removes the form and if necessary it's temporary row.
      */
@@ -634,7 +641,7 @@
 
     /*
     Called after an attachment file has been selected.
-    
+
     Updates the file name for the selected attachment.
      */
 
diff --git a/app/assets/stylesheets/framework/markdown_area.scss b/app/assets/stylesheets/framework/markdown_area.scss
index 96565da1bc9..edea4ad00eb 100644
--- a/app/assets/stylesheets/framework/markdown_area.scss
+++ b/app/assets/stylesheets/framework/markdown_area.scss
@@ -147,3 +147,8 @@
     color: $gl-link-color;
   }
 }
+
+.atwho-view small.description {
+  float: right;
+  padding: 3px 5px;
+}
diff --git a/app/controllers/projects/commit_controller.rb b/app/controllers/projects/commit_controller.rb
index f44e9bb3fd7..02fb3f56890 100644
--- a/app/controllers/projects/commit_controller.rb
+++ b/app/controllers/projects/commit_controller.rb
@@ -93,7 +93,7 @@ class Projects::CommitController < Projects::ApplicationController
   end
 
   def commit
-    @commit ||= @project.commit(params[:id])
+    @noteable = @commit ||= @project.commit(params[:id])
   end
 
   def pipelines
diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index e9fb11e8f94..639cf4c0ef2 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -177,11 +177,7 @@ class Projects::IssuesController < Projects::ApplicationController
   protected
 
   def issue
-    @issue ||= begin
-                 @project.issues.find_by!(iid: params[:id])
-               rescue ActiveRecord::RecordNotFound
-                 redirect_old
-               end
+    @noteable = @issue ||= @project.issues.find_by(iid: params[:id]) || redirect_old
   end
   alias_method :subscribable_resource, :issue
   alias_method :issuable, :issue
@@ -226,7 +222,6 @@ class Projects::IssuesController < Projects::ApplicationController
 
     if issue
       redirect_to issue_path(issue)
-      return
     else
       raise ActiveRecord::RecordNotFound.new
     end
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 4c1f38be9f3..0f52a5f96a3 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -381,7 +381,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   end
 
   def merge_request
-    @merge_request ||= @project.merge_requests.find_by!(iid: params[:id])
+    @issuable = @merge_request ||= @project.merge_requests.find_by!(iid: params[:id])
   end
   alias_method :subscribable_resource, :merge_request
   alias_method :issuable, :merge_request
diff --git a/app/controllers/projects/notes_controller.rb b/app/controllers/projects/notes_controller.rb
index 766b7e9cf22..f2422729364 100644
--- a/app/controllers/projects/notes_controller.rb
+++ b/app/controllers/projects/notes_controller.rb
@@ -125,7 +125,7 @@ class Projects::NotesController < Projects::ApplicationController
         id:     note.id,
         name:   note.name
       }
-    elsif note.valid?
+    elsif note.persisted?
       Banzai::NoteRenderer.render([note], @project, current_user)
 
       attrs = {
diff --git a/app/controllers/projects_controller.rb b/app/controllers/projects_controller.rb
index 47efbd4a939..fc52cd2f367 100644
--- a/app/controllers/projects_controller.rb
+++ b/app/controllers/projects_controller.rb
@@ -134,10 +134,22 @@ class ProjectsController < Projects::ApplicationController
   end
 
   def autocomplete_sources
-    note_type = params['type']
-    note_id = params['type_id']
+    noteable =
+      case params[:type]
+      when 'Issue'
+        IssuesFinder.new(current_user, project_id: @project.id, state: 'all').
+          execute.find_by(iid: params[:type_id])
+      when 'MergeRequest'
+        MergeRequestsFinder.new(current_user, project_id: @project.id, state: 'all').
+          execute.find_by(iid: params[:type_id])
+      when 'Commit'
+        @project.commit(params[:type_id])
+      else
+        nil
+      end
+
     autocomplete = ::Projects::AutocompleteService.new(@project, current_user)
-    participants = ::Projects::ParticipantsService.new(@project, current_user).execute(note_type, note_id)
+    participants = ::Projects::ParticipantsService.new(@project, current_user).execute(noteable)
 
     @suggestions = {
       emojis: Gitlab::AwardEmoji.urls,
@@ -145,7 +157,8 @@ class ProjectsController < Projects::ApplicationController
       milestones: autocomplete.milestones,
       mergerequests: autocomplete.merge_requests,
       labels: autocomplete.labels,
-      members: participants
+      members: participants,
+      commands: autocomplete.commands(noteable, params[:type])
     }
 
     respond_to do |format|
diff --git a/app/finders/todos_finder.rb b/app/finders/todos_finder.rb
index 4fe0070552e..37bad596a16 100644
--- a/app/finders/todos_finder.rb
+++ b/app/finders/todos_finder.rb
@@ -17,7 +17,7 @@ class TodosFinder
 
   attr_accessor :current_user, :params
 
-  def initialize(current_user, params)
+  def initialize(current_user, params = {})
     @current_user = current_user
     @params = params
   end
diff --git a/app/services/issuable_base_service.rb b/app/services/issuable_base_service.rb
index b0ea7c905f8..e06c37c323e 100644
--- a/app/services/issuable_base_service.rb
+++ b/app/services/issuable_base_service.rb
@@ -69,14 +69,9 @@ class IssuableBaseService < BaseService
   end
 
   def filter_labels
-    if params[:add_label_ids].present? || params[:remove_label_ids].present?
-      params.delete(:label_ids)
-
-      filter_labels_in_param(:add_label_ids)
-      filter_labels_in_param(:remove_label_ids)
-    else
-      filter_labels_in_param(:label_ids)
-    end
+    filter_labels_in_param(:add_label_ids)
+    filter_labels_in_param(:remove_label_ids)
+    filter_labels_in_param(:label_ids)
   end
 
   def filter_labels_in_param(key)
@@ -85,27 +80,86 @@ class IssuableBaseService < BaseService
     params[key] = project.labels.where(id: params[key]).pluck(:id)
   end
 
-  def update_issuable(issuable, attributes)
+  def process_label_ids(attributes, existing_label_ids: nil)
+    label_ids = attributes.delete(:label_ids)
+    add_label_ids = attributes.delete(:add_label_ids)
+    remove_label_ids = attributes.delete(:remove_label_ids)
+
+    new_label_ids = existing_label_ids || label_ids || []
+
+    if add_label_ids.blank? && remove_label_ids.blank?
+      new_label_ids = label_ids if label_ids
+    else
+      new_label_ids |= add_label_ids if add_label_ids
+      new_label_ids -= remove_label_ids if remove_label_ids
+    end
+
+    new_label_ids
+  end
+
+  def merge_slash_commands_into_params!(issuable)
+    description, command_params =
+      SlashCommands::InterpretService.new(project, current_user).
+      execute(params[:description], issuable)
+
+    params[:description] = description
+
+    params.merge!(command_params)
+  end
+
+  def create_issuable(issuable, attributes, label_ids:)
     issuable.with_transaction_returning_status do
-      add_label_ids = attributes.delete(:add_label_ids)
-      remove_label_ids = attributes.delete(:remove_label_ids)
+      if issuable.save
+        issuable.update_attributes(label_ids: label_ids)
+      end
+    end
+  end
 
-      issuable.label_ids |= add_label_ids if add_label_ids
-      issuable.label_ids -= remove_label_ids if remove_label_ids
+  def create(issuable)
+    merge_slash_commands_into_params!(issuable)
+    filter_params
+
+    params.delete(:state_event)
+    params[:author] ||= current_user
+    label_ids = process_label_ids(params)
+
+    issuable.assign_attributes(params)
+
+    before_create(issuable)
+
+    if params.present? && create_issuable(issuable, params, label_ids: label_ids)
+      after_create(issuable)
+      issuable.create_cross_references!(current_user)
+      execute_hooks(issuable)
+    end
+
+    issuable
+  end
 
-      issuable.assign_attributes(attributes.merge(updated_by: current_user))
+  def before_create(issuable)
+    # To be overridden by subclasses
+  end
+
+  def after_create(issuable)
+    # To be overridden by subclasses
+  end
 
-      issuable.save
+  def update_issuable(issuable, attributes)
+    issuable.with_transaction_returning_status do
+      issuable.update(attributes.merge(updated_by: current_user))
     end
   end
 
   def update(issuable)
     change_state(issuable)
     change_subscription(issuable)
+    change_todo(issuable)
     filter_params
     old_labels = issuable.labels.to_a
     old_mentioned_users = issuable.mentioned_users.to_a
 
+    params[:label_ids] = process_label_ids(params, existing_label_ids: issuable.label_ids)
+
     if params.present? && update_issuable(issuable, params)
       issuable.reset_events_cache
       handle_common_system_notes(issuable, old_labels: old_labels)
@@ -135,6 +189,16 @@ class IssuableBaseService < BaseService
     end
   end
 
+  def change_todo(issuable)
+    case params.delete(:todo_event)
+    when 'add'
+      todo_service.mark_todo(issuable, current_user)
+    when 'done'
+      todo = TodosFinder.new(current_user).execute.find_by(target: issuable)
+      todo_service.mark_todos_as_done([todo], current_user) if todo
+    end
+  end
+
   def has_changes?(issuable, old_labels: [])
     valid_attrs = [:title, :description, :assignee_id, :milestone_id, :target_branch]
 
diff --git a/app/services/issues/close_service.rb b/app/services/issues/close_service.rb
index 859c934ea3b..45cca216ccc 100644
--- a/app/services/issues/close_service.rb
+++ b/app/services/issues/close_service.rb
@@ -1,6 +1,8 @@
 module Issues
   class CloseService < Issues::BaseService
     def execute(issue, commit: nil, notifications: true, system_note: true)
+      return issue unless can?(current_user, :update_issue, issue)
+
       if project.jira_tracker? && project.jira_service.active
         project.jira_service.execute(commit, issue)
         todo_service.close_issue(issue, current_user)
diff --git a/app/services/issues/create_service.rb b/app/services/issues/create_service.rb
index 65550ab8ec6..ea1690f3e38 100644
--- a/app/services/issues/create_service.rb
+++ b/app/services/issues/create_service.rb
@@ -1,26 +1,23 @@
 module Issues
   class CreateService < Issues::BaseService
     def execute
-      filter_params
-      label_params = params.delete(:label_ids)
       @request = params.delete(:request)
       @api = params.delete(:api)
-      @issue = project.issues.new(params)
-      @issue.author = params[:author] || current_user
 
-      @issue.spam = spam_service.check(@api)
+      @issue = project.issues.new
 
-      if @issue.save
-        @issue.update_attributes(label_ids: label_params)
-        notification_service.new_issue(@issue, current_user)
-        todo_service.new_issue(@issue, current_user)
-        event_service.open_issue(@issue, current_user)
-        user_agent_detail_service.create
-        @issue.create_cross_references!(current_user)
-        execute_hooks(@issue, 'open')
-      end
+      create(@issue)
+    end
+
+    def before_create(issuable)
+      issuable.spam = spam_service.check(@api)
+    end
 
-      @issue
+    def after_create(issuable)
+      event_service.open_issue(issuable, current_user)
+      notification_service.new_issue(issuable, current_user)
+      todo_service.new_issue(issuable, current_user)
+      user_agent_detail_service.create
     end
 
     private
diff --git a/app/services/issues/reopen_service.rb b/app/services/issues/reopen_service.rb
index e48ca359f4f..40fbe354492 100644
--- a/app/services/issues/reopen_service.rb
+++ b/app/services/issues/reopen_service.rb
@@ -1,6 +1,8 @@
 module Issues
   class ReopenService < Issues::BaseService
     def execute(issue)
+      return issue unless can?(current_user, :update_issue, issue)
+
       if issue.reopen
         event_service.reopen_issue(issue, current_user)
         create_note(issue)
diff --git a/app/services/merge_requests/close_service.rb b/app/services/merge_requests/close_service.rb
index 27ee81fe3e7..f2053bda83a 100644
--- a/app/services/merge_requests/close_service.rb
+++ b/app/services/merge_requests/close_service.rb
@@ -1,6 +1,8 @@
 module MergeRequests
   class CloseService < MergeRequests::BaseService
     def execute(merge_request, commit = nil)
+      return merge_request unless can?(current_user, :update_merge_request, merge_request)
+
       # If we close MergeRequest we want to ignore validation
       # so we can close broken one (Ex. fork project removed)
       merge_request.allow_broken = true
diff --git a/app/services/merge_requests/create_service.rb b/app/services/merge_requests/create_service.rb
index 96a25330af1..73247e62421 100644
--- a/app/services/merge_requests/create_service.rb
+++ b/app/services/merge_requests/create_service.rb
@@ -7,26 +7,19 @@ module MergeRequests
       source_project = @project
       @project = Project.find(params[:target_project_id]) if params[:target_project_id]
 
-      filter_params
-      label_params = params.delete(:label_ids)
-      force_remove_source_branch = params.delete(:force_remove_source_branch)
+      params[:target_project_id] ||= source_project.id
 
-      merge_request = MergeRequest.new(params)
+      merge_request = MergeRequest.new
       merge_request.source_project = source_project
-      merge_request.target_project ||= source_project
-      merge_request.author = current_user
-      merge_request.merge_params['force_remove_source_branch'] = force_remove_source_branch
+      merge_request.merge_params['force_remove_source_branch'] = params.delete(:force_remove_source_branch)
 
-      if merge_request.save
-        merge_request.update_attributes(label_ids: label_params)
-        event_service.open_mr(merge_request, current_user)
-        notification_service.new_merge_request(merge_request, current_user)
-        todo_service.new_merge_request(merge_request, current_user)
-        merge_request.create_cross_references!(current_user)
-        execute_hooks(merge_request)
-      end
+      create(merge_request)
+    end
 
-      merge_request
+    def after_create(issuable)
+      event_service.open_mr(issuable, current_user)
+      notification_service.new_merge_request(issuable, current_user)
+      todo_service.new_merge_request(issuable, current_user)
     end
   end
 end
diff --git a/app/services/merge_requests/reopen_service.rb b/app/services/merge_requests/reopen_service.rb
index eb88ae9d11c..fadcce5d9b6 100644
--- a/app/services/merge_requests/reopen_service.rb
+++ b/app/services/merge_requests/reopen_service.rb
@@ -1,6 +1,8 @@
 module MergeRequests
   class ReopenService < MergeRequests::BaseService
     def execute(merge_request)
+      return merge_request unless can?(current_user, :update_merge_request, merge_request)
+
       if merge_request.reopen
         event_service.reopen_mr(merge_request, current_user)
         create_note(merge_request)
diff --git a/app/services/notes/create_service.rb b/app/services/notes/create_service.rb
index 18971bd0be3..a36008c3ef5 100644
--- a/app/services/notes/create_service.rb
+++ b/app/services/notes/create_service.rb
@@ -11,10 +11,33 @@ module Notes
         return noteable.create_award_emoji(note.award_emoji_name, current_user)
       end
 
-      if note.save
+      # We execute commands (extracted from `params[:note]`) on the noteable
+      # **before** we save the note because if the note consists of commands
+      # only, there is no need be create a note!
+      slash_commands_service = SlashCommandsService.new(project, current_user)
+
+      if slash_commands_service.supported?(note)
+        content, command_params = slash_commands_service.extract_commands(note)
+
+        only_commands = content.empty?
+
+        note.note = content
+      end
+
+      if !only_commands && note.save
         # Finish the harder work in the background
         NewNoteWorker.perform_in(2.seconds, note.id, params)
-        TodoService.new.new_note(note, current_user)
+        todo_service.new_note(note, current_user)
+      end
+
+      if command_params && command_params.any?
+        slash_commands_service.execute(command_params, note)
+
+        # We must add the error after we call #save because errors are reset
+        # when #save is called
+        if only_commands
+          note.errors.add(:commands_only, 'Your commands have been executed!')
+        end
       end
 
       note
diff --git a/app/services/notes/slash_commands_service.rb b/app/services/notes/slash_commands_service.rb
new file mode 100644
index 00000000000..4a9a8a64653
--- /dev/null
+++ b/app/services/notes/slash_commands_service.rb
@@ -0,0 +1,33 @@
+module Notes
+  class SlashCommandsService < BaseService
+    UPDATE_SERVICES = {
+      'Issue' => Issues::UpdateService,
+      'MergeRequest' => MergeRequests::UpdateService
+    }
+
+    def supported?(note)
+      noteable_update_service(note) &&
+        can?(current_user, :"update_#{note.noteable_type.underscore}", note.noteable)
+    end
+
+    def extract_commands(note)
+      return [note.note, {}] unless supported?(note)
+
+      SlashCommands::InterpretService.new(project, current_user).
+        execute(note.note, note.noteable)
+    end
+
+    def execute(command_params, note)
+      return if command_params.empty?
+      return unless supported?(note)
+
+      noteable_update_service(note).new(project, current_user, command_params).execute(note.noteable)
+    end
+
+    private
+
+    def noteable_update_service(note)
+      UPDATE_SERVICES[note.noteable_type]
+    end
+  end
+end
diff --git a/app/services/projects/autocomplete_service.rb b/app/services/projects/autocomplete_service.rb
index 23b6668e0d1..f578f8dbea2 100644
--- a/app/services/projects/autocomplete_service.rb
+++ b/app/services/projects/autocomplete_service.rb
@@ -1,7 +1,7 @@
 module Projects
   class AutocompleteService < BaseService
     def issues
-      @project.issues.visible_to_user(current_user).opened.select([:iid, :title])
+      IssuesFinder.new(current_user, project_id: project.id, state: 'opened').execute.select([:iid, :title])
     end
 
     def milestones
@@ -9,11 +9,34 @@ module Projects
     end
 
     def merge_requests
-      @project.merge_requests.opened.select([:iid, :title])
+      MergeRequestsFinder.new(current_user, project_id: project.id, state: 'opened').execute.select([:iid, :title])
     end
 
     def labels
       @project.labels.select([:title, :color])
     end
+
+    def commands(noteable, type)
+      noteable ||=
+        case type
+        when 'Issue'
+          @project.issues.build
+        when 'MergeRequest'
+          @project.merge_requests.build
+        end
+
+      return [] unless noteable && noteable.is_a?(Issuable)
+
+      opts = {
+        project: project,
+        issuable: noteable,
+        current_user: current_user
+      }
+      SlashCommands::InterpretService.command_definitions.map do |definition|
+        next unless definition.available?(opts)
+
+        definition.to_h(opts)
+      end.compact
+    end
   end
 end
diff --git a/app/services/projects/participants_service.rb b/app/services/projects/participants_service.rb
index 02c4eee3d02..d38328403c1 100644
--- a/app/services/projects/participants_service.rb
+++ b/app/services/projects/participants_service.rb
@@ -1,40 +1,28 @@
 module Projects
   class ParticipantsService < BaseService
-    def execute(noteable_type, noteable_id)
-      @noteable_type = noteable_type
-      @noteable_id = noteable_id
+    attr_reader :noteable
+    
+    def execute(noteable)
+      @noteable = noteable
+
       project_members = sorted(project.team.members)
-      participants = target_owner + participants_in_target + all_members + groups + project_members
+      participants = noteable_owner + participants_in_noteable + all_members + groups + project_members
       participants.uniq
     end
 
-    def target
-      @target ||=
-        case @noteable_type
-        when "Issue"
-          project.issues.find_by_iid(@noteable_id)
-        when "MergeRequest"
-          project.merge_requests.find_by_iid(@noteable_id)
-        when "Commit"
-          project.commit(@noteable_id)
-        else
-          nil
-        end
-    end
-
-    def target_owner
-      return [] unless target && target.author.present?
+    def noteable_owner
+      return [] unless noteable && noteable.author.present?
 
       [{
-        name: target.author.name,
-        username: target.author.username
+        name: noteable.author.name,
+        username: noteable.author.username
       }]
     end
 
-    def participants_in_target
-      return [] unless target
+    def participants_in_noteable
+      return [] unless noteable
 
-      users = target.participants(current_user)
+      users = noteable.participants(current_user)
       sorted(users)
     end
 
diff --git a/app/services/slash_commands/interpret_service.rb b/app/services/slash_commands/interpret_service.rb
new file mode 100644
index 00000000000..9ac1124abc1
--- /dev/null
+++ b/app/services/slash_commands/interpret_service.rb
@@ -0,0 +1,236 @@
+module SlashCommands
+  class InterpretService < BaseService
+    include Gitlab::SlashCommands::Dsl
+
+    attr_reader :issuable
+
+    # Takes a text and interprets the commands that are extracted from it.
+    # Returns the content without commands, and hash of changes to be applied to a record.
+    def execute(content, issuable)
+      @issuable = issuable
+      @updates = {}
+
+      opts = {
+        issuable:     issuable,
+        current_user: current_user,
+        project:      project
+      }
+
+      content, commands = extractor.extract_commands(content, opts)
+
+      commands.each do |name, arg|
+        definition = self.class.command_definitions_by_name[name.to_sym]
+        next unless definition
+
+        definition.execute(self, opts, arg)
+      end
+
+      [content, @updates]
+    end
+
+    private
+
+    def extractor
+      Gitlab::SlashCommands::Extractor.new(self.class.command_definitions)
+    end
+
+    desc do
+      "Close this #{issuable.to_ability_name.humanize(capitalize: false)}"
+    end
+    condition do
+      issuable.persisted? &&
+        issuable.open? &&
+        current_user.can?(:"update_#{issuable.to_ability_name}", issuable)
+    end
+    command :close do
+      @updates[:state_event] = 'close'
+    end
+
+    desc do
+      "Reopen this #{issuable.to_ability_name.humanize(capitalize: false)}"
+    end
+    condition do
+      issuable.persisted? &&
+        issuable.closed? &&
+        current_user.can?(:"update_#{issuable.to_ability_name}", issuable)
+    end
+    command :reopen do
+      @updates[:state_event] = 'reopen'
+    end
+
+    desc 'Change title'
+    params '<New title>'
+    condition do
+      issuable.persisted? &&
+        current_user.can?(:"update_#{issuable.to_ability_name}", issuable)
+    end
+    command :title do |title_param|
+      @updates[:title] = title_param
+    end
+
+    desc 'Assign'
+    params '@user'
+    condition do
+      current_user.can?(:"admin_#{issuable.to_ability_name}", project)
+    end
+    command :assign do |assignee_param|
+      user = extract_references(assignee_param, :user).first
+      user ||= User.find_by(username: assignee_param)
+
+      @updates[:assignee_id] = user.id if user
+    end
+
+    desc 'Remove assignee'
+    condition do
+      issuable.persisted? &&
+        issuable.assignee_id? &&
+        current_user.can?(:"admin_#{issuable.to_ability_name}", project)
+    end
+    command :unassign do
+      @updates[:assignee_id] = nil
+    end
+
+    desc 'Set milestone'
+    params '%"milestone"'
+    condition do
+      current_user.can?(:"admin_#{issuable.to_ability_name}", project) &&
+        project.milestones.active.any?
+    end
+    command :milestone do |milestone_param|
+      milestone = extract_references(milestone_param, :milestone).first
+      milestone ||= project.milestones.find_by(title: milestone_param.strip)
+
+      @updates[:milestone_id] = milestone.id if milestone
+    end
+
+    desc 'Remove milestone'
+    condition do
+      issuable.persisted? &&
+        issuable.milestone_id? &&
+        current_user.can?(:"admin_#{issuable.to_ability_name}", project)
+    end
+    command :remove_milestone do
+      @updates[:milestone_id] = nil
+    end
+
+    desc 'Add label(s)'
+    params '~label1 ~"label 2"'
+    condition do
+      current_user.can?(:"admin_#{issuable.to_ability_name}", project) &&
+        project.labels.any?
+    end
+    command :label do |labels_param|
+      label_ids = find_label_ids(labels_param)
+
+      @updates[:add_label_ids] = label_ids unless label_ids.empty?
+    end
+
+    desc 'Remove all or specific label(s)'
+    params '~label1 ~"label 2"'
+    condition do
+      issuable.persisted? &&
+        issuable.labels.any? &&
+        current_user.can?(:"admin_#{issuable.to_ability_name}", project)
+    end
+    command :unlabel do |labels_param = nil|
+      if labels_param.present?
+        label_ids = find_label_ids(labels_param)
+
+        @updates[:remove_label_ids] = label_ids unless label_ids.empty?
+      else
+        @updates[:label_ids] = []
+      end
+    end
+
+    desc 'Replace all label(s)'
+    params '~label1 ~"label 2"'
+    condition do
+      issuable.persisted? &&
+        issuable.labels.any? &&
+        current_user.can?(:"admin_#{issuable.to_ability_name}", project)
+    end
+    command :relabel do |labels_param|
+      label_ids = find_label_ids(labels_param)
+
+      @updates[:label_ids] = label_ids unless label_ids.empty?
+    end
+
+    desc 'Add a todo'
+    condition do
+      issuable.persisted? &&
+        !TodoService.new.todo_exist?(issuable, current_user)
+    end
+    command :todo do
+      @updates[:todo_event] = 'add'
+    end
+
+    desc 'Mark todo as done'
+    condition do
+      issuable.persisted? &&
+        TodoService.new.todo_exist?(issuable, current_user)
+    end
+    command :done do
+      @updates[:todo_event] = 'done'
+    end
+
+    desc 'Subscribe'
+    condition do
+      issuable.persisted? &&
+        !issuable.subscribed?(current_user)
+    end
+    command :subscribe do
+      @updates[:subscription_event] = 'subscribe'
+    end
+
+    desc 'Unsubscribe'
+    condition do
+      issuable.persisted? &&
+        issuable.subscribed?(current_user)
+    end
+    command :unsubscribe do
+      @updates[:subscription_event] = 'unsubscribe'
+    end
+
+    desc 'Set due date'
+    params '<in 2 days | this Friday | December 31st>'
+    condition do
+      issuable.respond_to?(:due_date) &&
+        current_user.can?(:"update_#{issuable.to_ability_name}", issuable)
+    end
+    command :due do |due_date_param|
+      due_date = Chronic.parse(due_date_param).try(:to_date)
+
+      @updates[:due_date] = due_date if due_date
+    end
+
+    desc 'Remove due date'
+    condition do
+      issuable.persisted? &&
+        issuable.respond_to?(:due_date) &&
+        issuable.due_date? &&
+        current_user.can?(:"update_#{issuable.to_ability_name}", issuable)
+    end
+    command :remove_due_date do
+      @updates[:due_date] = nil
+    end
+
+    # This is a dummy command, so that it appears in the autocomplete commands
+    desc 'CC'
+    params '@user'
+    command :cc
+
+    def find_label_ids(labels_param)
+      label_ids_by_reference = extract_references(labels_param, :label).map(&:id)
+      labels_ids_by_name = @project.labels.where(name: labels_param.split).select(:id)
+
+      label_ids_by_reference | labels_ids_by_name
+    end
+
+    def extract_references(arg, type)
+      ext = Gitlab::ReferenceExtractor.new(project, current_user)
+      ext.analyze(arg, author: current_user)
+
+      ext.references(type)
+    end
+  end
+end
diff --git a/app/services/todo_service.rb b/app/services/todo_service.rb
index daf4339cb48..e0ccb654590 100644
--- a/app/services/todo_service.rb
+++ b/app/services/todo_service.rb
@@ -159,6 +159,10 @@ class TodoService
     create_todos(current_user, attributes)
   end
 
+  def todo_exist?(issuable, current_user)
+    TodosFinder.new(current_user).execute.exists?(target: issuable)
+  end
+
   private
 
   def create_todos(users, attributes)
diff --git a/app/views/layouts/_init_auto_complete.html.haml b/app/views/layouts/_init_auto_complete.html.haml
index 351100f3523..67ff4b272b9 100644
--- a/app/views/layouts/_init_auto_complete.html.haml
+++ b/app/views/layouts/_init_auto_complete.html.haml
@@ -1,7 +1,7 @@
 - project = @target_project || @project
-- noteable_class = @noteable.class if @noteable.present?
+- noteable_type = @noteable.class if @noteable.present?
 
 :javascript
-  GitLab.GfmAutoComplete.dataSource = "#{autocomplete_sources_namespace_project_path(project.namespace, project, type: noteable_class, type_id: params[:id])}"
+  GitLab.GfmAutoComplete.dataSource = "#{autocomplete_sources_namespace_project_path(project.namespace, project, type: noteable_type, type_id: params[:id])}"
   GitLab.GfmAutoComplete.cachedData = undefined;
   GitLab.GfmAutoComplete.setup();
diff --git a/app/views/projects/_zen.html.haml b/app/views/projects/_zen.html.haml
index 413477a2d3a..3978fa60d66 100644
--- a/app/views/projects/_zen.html.haml
+++ b/app/views/projects/_zen.html.haml
@@ -1,7 +1,8 @@
+- supports_slash_commands = local_assigns.fetch(:supports_slash_commands, false)
 .zen-backdrop
   - classes << ' js-gfm-input js-autosize markdown-area'
   - if defined?(f) && f
-    = f.text_area attr, class: classes, placeholder: placeholder
+    = f.text_area attr, class: classes, placeholder: placeholder, data: { supports_slash_commands: supports_slash_commands }
   - else
     = text_area_tag attr, nil, class: classes, placeholder: placeholder
   %a.zen-control.zen-control-leave.js-zen-leave{ href: "#" }
diff --git a/app/views/projects/notes/_form.html.haml b/app/views/projects/notes/_form.html.haml
index 7c61ba750fe..759c72b2477 100644
--- a/app/views/projects/notes/_form.html.haml
+++ b/app/views/projects/notes/_form.html.haml
@@ -10,8 +10,12 @@
   = f.hidden_field :position
 
   = render layout: 'projects/md_preview', locals: { preview_class: "md-preview", referenced_users: true } do
-    = render 'projects/zen', f: f, attr: :note, classes: 'note-textarea js-note-text', placeholder: "Write a comment or drag your files here..."
-    = render 'projects/notes/hints'
+    = render 'projects/zen', f: f,
+      attr: :note,
+      classes: 'note-textarea js-note-text',
+      placeholder: "Write a comment or drag your files here...",
+      supports_slash_commands: true
+    = render 'projects/notes/hints', supports_slash_commands: true
     .error-alert
 
   .note-form-actions.clearfix
diff --git a/app/views/projects/notes/_hints.html.haml b/app/views/projects/notes/_hints.html.haml
index 25466e7562e..cf6e14648cc 100644
--- a/app/views/projects/notes/_hints.html.haml
+++ b/app/views/projects/notes/_hints.html.haml
@@ -1,8 +1,15 @@
+- supports_slash_commands = local_assigns.fetch(:supports_slash_commands, false)
 .comment-toolbar.clearfix
   .toolbar-text
     Styling with
     = link_to 'Markdown', help_page_path('markdown/markdown'), target: '_blank', tabindex: -1
-    is supported
+    - if supports_slash_commands
+      and
+      = link_to 'slash commands', help_page_path('workflow/slash_commands'), target: '_blank', tabindex: -1
+      are
+    - else
+      is
+    supported
   %button.toolbar-button.markdown-selector{ type: 'button', tabindex: '-1' }
     = icon('file-image-o', class: 'toolbar-button-icon')
-    Attach a file
\ No newline at end of file
+    Attach a file
diff --git a/app/views/shared/issuable/_form.html.haml b/app/views/shared/issuable/_form.html.haml
index c30bdb0ae91..25b29ccf70d 100644
--- a/app/views/shared/issuable/_form.html.haml
+++ b/app/views/shared/issuable/_form.html.haml
@@ -30,8 +30,9 @@
     = render layout: 'projects/md_preview', locals: { preview_class: "md-preview", referenced_users: true } do
       = render 'projects/zen', f: f, attr: :description,
                                classes: 'note-textarea',
-                               placeholder: "Write a comment or drag your files here..."
-      = render 'projects/notes/hints'
+                               placeholder: "Write a comment or drag your files here...",
+                               supports_slash_commands: !issuable.persisted?
+      = render 'projects/notes/hints', supports_slash_commands: !issuable.persisted?
       .clearfix
       .error-alert
 
diff --git a/doc/workflow/README.md b/doc/workflow/README.md
index 49dec613716..17c04377b4c 100644
--- a/doc/workflow/README.md
+++ b/doc/workflow/README.md
@@ -6,6 +6,7 @@
 - [GitLab Flow](gitlab_flow.md)
 - [Groups](groups.md)
 - [Keyboard shortcuts](shortcuts.md)
+- [Slash commands](slash_commands.md)
 - [File finder](file_finder.md)
 - [Labels](../user/project/labels.md)
 - [Notification emails](notifications.md)
diff --git a/doc/workflow/slash_commands.md b/doc/workflow/slash_commands.md
new file mode 100644
index 00000000000..91d69d4e77e
--- /dev/null
+++ b/doc/workflow/slash_commands.md
@@ -0,0 +1,30 @@
+# GitLab slash commands
+
+Slash commands are textual shortcuts for common actions on issues or merge
+requests that are usually done by clicking buttons or dropdowns in GitLab's UI.
+You can enter these commands while creating a new issue or merge request, and
+in comments. Each command should be on a separate line in order to be properly
+detected and executed. The commands are removed from the issue, merge request or
+comment body before it is saved and will not be visible to anyone else.
+
+Below is a list of all of the available commands and descriptions about what they
+do.
+
+| Command                    | Action       |
+|:---------------------------|:-------------|
+| `/close`                   | Close the issue or merge request |
+| `/reopen`                  | Reopen the issue or merge request |
+| `/title <New title>`       | Change title |
+| `/assign @username`        | Assign |
+| `/unassign`                | Remove assignee |
+| `/milestone %milestone`    | Set milestone |
+| `/remove_milestone`        | Remove milestone |
+| `/label ~foo ~"bar baz"`   | Add label(s) |
+| `/unlabel ~foo ~"bar baz"` | Remove all or specific label(s) |
+| `/relabel ~foo ~"bar baz"` | Replace all label(s) |
+| `/todo`                    | Add a todo |
+| `/done`                    | Mark todo as done |
+| `/subscribe`               | Subscribe |
+| `/unsubscribe`             | Unsubscribe |
+| `/due <in 2 days | this Friday | December 31st>` | Set due date |
+| `/remove_due_date`          | Remove due date |
diff --git a/lib/gitlab/email/handler/base_handler.rb b/lib/gitlab/email/handler/base_handler.rb
index b7ed11cb638..7cccf465334 100644
--- a/lib/gitlab/email/handler/base_handler.rb
+++ b/lib/gitlab/email/handler/base_handler.rb
@@ -45,6 +45,7 @@ module Gitlab
 
         def verify_record!(record:, invalid_exception:, record_name:)
           return if record.persisted?
+          return if record.errors.key?(:commands_only)
 
           error_title = "The #{record_name} could not be created for the following reasons:"
 
diff --git a/lib/gitlab/slash_commands/command_definition.rb b/lib/gitlab/slash_commands/command_definition.rb
new file mode 100644
index 00000000000..60d35be2599
--- /dev/null
+++ b/lib/gitlab/slash_commands/command_definition.rb
@@ -0,0 +1,57 @@
+module Gitlab
+  module SlashCommands
+    class CommandDefinition
+      attr_accessor :name, :aliases, :description, :params, :condition_block, :action_block
+
+      def initialize(name, attributes = {})
+        @name = name
+
+        @aliases         = attributes[:aliases] || []
+        @description     = attributes[:description] || ''
+        @params          = attributes[:params] || []
+        @condition_block = attributes[:condition_block]
+        @action_block    = attributes[:action_block]
+      end
+
+      def all_names
+        [name, *aliases]
+      end
+
+      def noop?
+        action_block.nil?
+      end
+
+      def available?(opts)
+        return true unless condition_block
+
+        context = OpenStruct.new(opts)
+        context.instance_exec(&condition_block)
+      end
+
+      def execute(context, opts, arg)
+        return if noop? || !available?(opts)
+
+        if arg.present?
+          context.instance_exec(arg, &action_block)
+        elsif action_block.arity == 0
+          context.instance_exec(&action_block)
+        end
+      end
+
+      def to_h(opts)
+        desc = description
+        if desc.respond_to?(:call)
+          context = OpenStruct.new(opts)
+          desc = context.instance_exec(&desc) rescue ''
+        end
+
+        {
+          name: name,
+          aliases: aliases,
+          description: desc,
+          params: params
+        }
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/slash_commands/dsl.rb b/lib/gitlab/slash_commands/dsl.rb
new file mode 100644
index 00000000000..50b0937d267
--- /dev/null
+++ b/lib/gitlab/slash_commands/dsl.rb
@@ -0,0 +1,98 @@
+module Gitlab
+  module SlashCommands
+    module Dsl
+      extend ActiveSupport::Concern
+
+      included do
+        cattr_accessor :command_definitions, instance_accessor: false do
+          []
+        end
+
+        cattr_accessor :command_definitions_by_name, instance_accessor: false do
+          {}
+        end
+      end
+
+      class_methods do
+        # Allows to give a description to the next slash command.
+        # This description is shown in the autocomplete menu.
+        # It accepts a block that will be evaluated with the context given to
+        # `CommandDefintion#to_h`.
+        #
+        # Example:
+        #
+        #   desc do
+        #     "This is a dynamic description for #{noteable.to_ability_name}"
+        #   end
+        #   command :command_key do |arguments|
+        #     # Awesome code block
+        #   end
+        def desc(text = '', &block)
+          @description = block_given? ? block : text
+        end
+
+        # Allows to define params for the next slash command.
+        # These params are shown in the autocomplete menu.
+        #
+        # Example:
+        #
+        #   params "~label ~label2"
+        #   command :command_key do |arguments|
+        #     # Awesome code block
+        #   end
+        def params(*params)
+          @params = params
+        end
+
+        # Allows to define conditions that must be met in order for the command
+        # to be returned by `.command_names` & `.command_definitions`.
+        # It accepts a block that will be evaluated with the context given to
+        # `CommandDefintion#to_h`.
+        #
+        # Example:
+        #
+        #   condition do
+        #     project.public?
+        #   end
+        #   command :command_key do |arguments|
+        #     # Awesome code block
+        #   end
+        def condition(&block)
+          @condition_block = block
+        end
+
+        # Registers a new command which is recognizeable from body of email or
+        # comment.
+        # It accepts aliases and takes a block.
+        #
+        # Example:
+        #
+        #   command :my_command, :alias_for_my_command do |arguments|
+        #     # Awesome code block
+        #   end
+        def command(*command_names, &block)
+          name, *aliases = command_names
+
+          definition = CommandDefinition.new(
+            name,
+            aliases:          aliases,
+            description:      @description,
+            params:           @params,
+            condition_block:  @condition_block,
+            action_block:     block
+          )
+
+          self.command_definitions << definition
+
+          definition.all_names.each do |name|
+            self.command_definitions_by_name[name] = definition
+          end
+
+          @description = nil
+          @params = nil
+          @condition_block = nil
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/slash_commands/extractor.rb b/lib/gitlab/slash_commands/extractor.rb
new file mode 100644
index 00000000000..a672e5e4855
--- /dev/null
+++ b/lib/gitlab/slash_commands/extractor.rb
@@ -0,0 +1,122 @@
+module Gitlab
+  module SlashCommands
+    # This class takes an array of commands that should be extracted from a
+    # given text.
+    #
+    # ```
+    # extractor = Gitlab::SlashCommands::Extractor.new([:open, :assign, :labels])
+    # ```
+    class Extractor
+      attr_reader :command_definitions
+
+      def initialize(command_definitions)
+        @command_definitions = command_definitions
+      end
+
+      # Extracts commands from content and return an array of commands.
+      # The array looks like the following:
+      # [
+      #   ['command1'],
+      #   ['command3', 'arg1 arg2'],
+      # ]
+      # The command and the arguments are stripped.
+      # The original command text is removed from the given `content`.
+      #
+      # Usage:
+      # ```
+      # extractor = Gitlab::SlashCommands::Extractor.new([:open, :assign, :labels])
+      # msg = %(hello\n/labels ~foo ~"bar baz"\nworld)
+      # commands = extractor.extract_commands(msg) #=> [['labels', '~foo ~"bar baz"']]
+      # msg #=> "hello\nworld"
+      # ```
+      def extract_commands(content, opts = {})
+        return [content, []] unless content
+
+        content = content.dup
+
+        commands = []
+
+        content.delete!("\r")
+        content.gsub!(commands_regex(opts)) do
+          if $~[:cmd]
+            commands << [$~[:cmd], $~[:arg]].reject(&:blank?)
+            ''
+          else
+            $~[0]
+          end
+        end
+
+        [content.strip, commands]
+      end
+
+      private
+
+      # Builds a regular expression to match known commands.
+      # First match group captures the command name and
+      # second match group captures its arguments.
+      #
+      # It looks something like:
+      #
+      #   /^\/(?<cmd>close|reopen|...)(?:( |$))(?<arg>[^\/\n]*)(?:\n|$)/
+      def commands_regex(opts)
+        names = command_names(opts).map(&:to_s)
+
+        @commands_regex ||= %r{
+            (?<code>
+              # Code blocks:
+              # ```
+              # Anything, including `/cmd arg` which are ignored by this filter
+              # ```
+
+              ^```
+              .+?
+              \n```$
+            )
+          |
+            (?<html>
+              # HTML block:
+              # <tag>
+              # Anything, including `/cmd arg` which are ignored by this filter
+              # </tag>
+
+              ^<[^>]+?>\n
+              .+?
+              \n<\/[^>]+?>$
+            )
+          |
+            (?<html>
+              # Quote block:
+              # >>>
+              # Anything, including `/cmd arg` which are ignored by this filter
+              # >>>
+
+              ^>>>
+              .+?
+              \n>>>$
+            )
+          |
+            (?:
+              # Command not in a blockquote, blockcode, or HTML tag:
+              # /close
+
+              ^\/
+              (?<cmd>#{Regexp.union(names)})
+              (?:
+                [ ]
+                (?<arg>[^\/\n]*)
+              )?
+              (?:\n|$)
+            )
+        }mx
+      end
+
+      def command_names(opts)
+        command_definitions.flat_map do |command|
+          next if command.noop?
+
+          command.all_names
+        end.compact
+      end
+    end
+  end
+end
diff --git a/spec/features/issues/user_uses_slash_commands_spec.rb b/spec/features/issues/user_uses_slash_commands_spec.rb
new file mode 100644
index 00000000000..2883e392694
--- /dev/null
+++ b/spec/features/issues/user_uses_slash_commands_spec.rb
@@ -0,0 +1,58 @@
+require 'rails_helper'
+
+feature 'Issues > User uses slash commands', feature: true, js: true do
+  include WaitForAjax
+
+  it_behaves_like 'issuable record that supports slash commands in its description and notes', :issue do
+    let(:issuable) { create(:issue, project: project) }
+  end
+
+  describe 'issue-only commands' do
+    let(:user) { create(:user) }
+    let(:project) { create(:project, :public) }
+
+    before do
+      project.team << [user, :master]
+      login_with(user)
+      visit namespace_project_issue_path(project.namespace, project, issue)
+    end
+
+    describe 'adding a due date from note' do
+      let(:issue) { create(:issue, project: project) }
+
+      it 'does not create a note, and sets the due date accordingly' do
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "/due 2016-08-28"
+          click_button 'Comment'
+        end
+
+        expect(page).not_to have_content '/due 2016-08-28'
+        expect(page).to have_content 'Your commands have been executed!'
+
+        issue.reload
+
+        expect(issue.due_date).to eq Date.new(2016, 8, 28)
+      end
+    end
+
+    describe 'removing a due date from note' do
+      let(:issue) { create(:issue, project: project, due_date: Date.new(2016, 8, 28)) }
+
+      it 'does not create a note, and removes the due date accordingly' do
+        expect(issue.due_date).to eq Date.new(2016, 8, 28)
+
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "/remove_due_date"
+          click_button 'Comment'
+        end
+
+        expect(page).not_to have_content '/remove_due_date'
+        expect(page).to have_content 'Your commands have been executed!'
+
+        issue.reload
+
+        expect(issue.due_date).to be_nil
+      end
+    end
+  end
+end
diff --git a/spec/features/merge_requests/user_uses_slash_commands_spec.rb b/spec/features/merge_requests/user_uses_slash_commands_spec.rb
new file mode 100644
index 00000000000..d9ef0d18074
--- /dev/null
+++ b/spec/features/merge_requests/user_uses_slash_commands_spec.rb
@@ -0,0 +1,32 @@
+require 'rails_helper'
+
+feature 'Merge Requests > User uses slash commands', feature: true, js: true do
+  include WaitForAjax
+
+  let(:user) { create(:user) }
+  let(:project) { create(:project, :public) }
+  let(:merge_request) { create(:merge_request, source_project: project) }
+  let!(:milestone) { create(:milestone, project: project, title: 'ASAP') }
+
+  it_behaves_like 'issuable record that supports slash commands in its description and notes', :merge_request do
+    let(:issuable) { create(:merge_request, source_project: project) }
+    let(:new_url_opts) { { merge_request: { source_branch: 'feature' } } }
+  end
+
+  describe 'adding a due date from note' do
+    before do
+      project.team << [user, :master]
+      login_with(user)
+      visit namespace_project_merge_request_path(project.namespace, project, merge_request)
+    end
+
+    it 'does not recognize the command nor create a note' do
+      page.within('.js-main-target-form') do
+        fill_in 'note[note]', with: "/due 2016-08-28"
+        click_button 'Comment'
+      end
+
+      expect(page).not_to have_content '/due 2016-08-28'
+    end
+  end
+end
diff --git a/spec/fixtures/emails/commands_in_reply.eml b/spec/fixtures/emails/commands_in_reply.eml
new file mode 100644
index 00000000000..06bf60ab734
--- /dev/null
+++ b/spec/fixtures/emails/commands_in_reply.eml
@@ -0,0 +1,43 @@
+Return-Path: <jake@adventuretime.ooo>
+Received: from iceking.adventuretime.ooo ([unix socket]) by iceking (Cyrus v2.2.13-Debian-2.2.13-19+squeeze3) with LMTPA; Thu, 13 Jun 2013 17:03:50 -0400
+Received: from mail-ie0-x234.google.com (mail-ie0-x234.google.com [IPv6:2607:f8b0:4001:c03::234]) by iceking.adventuretime.ooo (8.14.3/8.14.3/Debian-9.4) with ESMTP id r5DL3nFJ016967 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for <reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo>; Thu, 13 Jun 2013 17:03:50 -0400
+Received: by mail-ie0-f180.google.com with SMTP id f4so21977375iea.25 for <reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo>; Thu, 13 Jun 2013 14:03:48 -0700
+Received: by 10.0.0.1 with HTTP; Thu, 13 Jun 2013 14:03:48 -0700
+Date: Thu, 13 Jun 2013 17:03:48 -0400
+From: Jake the Dog <jake@adventuretime.ooo>
+To: reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo
+Message-ID: <CADkmRc+rNGAGGbV2iE5p918UVy4UyJqVcXRO2=otppgzduJSg@mail.gmail.com>
+In-Reply-To: <issue_1@localhost>
+References: <issue_1@localhost> <reply-59d8df8370b7e95c5a49fbf86aeb2c93@localhost>
+Subject: re: [Discourse Meta] eviltrout posted in 'Adventure Time Sux'
+Mime-Version: 1.0
+Content-Type: text/plain;
+ charset=ISO-8859-1
+Content-Transfer-Encoding: 7bit
+X-Sieve: CMU Sieve 2.2
+X-Received: by 10.0.0.1 with SMTP id n7mr11234144ipb.85.1371157428600; Thu,
+ 13 Jun 2013 14:03:48 -0700 (PDT)
+X-Scanned-By: MIMEDefang 2.69 on IPv6:2001:470:1d:165::1
+
+Cool!
+
+/close
+/todo
+/due tomorrow
+
+
+On Sun, Jun 9, 2013 at 1:39 PM, eviltrout via Discourse Meta
+<reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo> wrote:
+>
+>
+>
+> eviltrout posted in 'Adventure Time Sux' on Discourse Meta:
+>
+> ---
+> hey guys everyone knows adventure time sucks!
+>
+> ---
+> Please visit this link to respond: http://localhost:3000/t/adventure-time-sux/1234/3
+>
+> To unsubscribe from these emails, visit your [user preferences](http://localhost:3000/user_preferences).
+>
diff --git a/spec/fixtures/emails/commands_only_reply.eml b/spec/fixtures/emails/commands_only_reply.eml
new file mode 100644
index 00000000000..aed64224b06
--- /dev/null
+++ b/spec/fixtures/emails/commands_only_reply.eml
@@ -0,0 +1,41 @@
+Return-Path: <jake@adventuretime.ooo>
+Received: from iceking.adventuretime.ooo ([unix socket]) by iceking (Cyrus v2.2.13-Debian-2.2.13-19+squeeze3) with LMTPA; Thu, 13 Jun 2013 17:03:50 -0400
+Received: from mail-ie0-x234.google.com (mail-ie0-x234.google.com [IPv6:2607:f8b0:4001:c03::234]) by iceking.adventuretime.ooo (8.14.3/8.14.3/Debian-9.4) with ESMTP id r5DL3nFJ016967 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for <reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo>; Thu, 13 Jun 2013 17:03:50 -0400
+Received: by mail-ie0-f180.google.com with SMTP id f4so21977375iea.25 for <reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo>; Thu, 13 Jun 2013 14:03:48 -0700
+Received: by 10.0.0.1 with HTTP; Thu, 13 Jun 2013 14:03:48 -0700
+Date: Thu, 13 Jun 2013 17:03:48 -0400
+From: Jake the Dog <jake@adventuretime.ooo>
+To: reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo
+Message-ID: <CADkmRc+rNGAGGbV2iE5p918UVy4UyJqVcXRO2=otppgzduJSg@mail.gmail.com>
+In-Reply-To: <issue_1@localhost>
+References: <issue_1@localhost> <reply-59d8df8370b7e95c5a49fbf86aeb2c93@localhost>
+Subject: re: [Discourse Meta] eviltrout posted in 'Adventure Time Sux'
+Mime-Version: 1.0
+Content-Type: text/plain;
+ charset=ISO-8859-1
+Content-Transfer-Encoding: 7bit
+X-Sieve: CMU Sieve 2.2
+X-Received: by 10.0.0.1 with SMTP id n7mr11234144ipb.85.1371157428600; Thu,
+ 13 Jun 2013 14:03:48 -0700 (PDT)
+X-Scanned-By: MIMEDefang 2.69 on IPv6:2001:470:1d:165::1
+
+/close
+/todo
+/due tomorrow
+
+
+On Sun, Jun 9, 2013 at 1:39 PM, eviltrout via Discourse Meta
+<reply+59d8df8370b7e95c5a49fbf86aeb2c93@appmail.adventuretime.ooo> wrote:
+>
+>
+>
+> eviltrout posted in 'Adventure Time Sux' on Discourse Meta:
+>
+> ---
+> hey guys everyone knows adventure time sucks!
+>
+> ---
+> Please visit this link to respond: http://localhost:3000/t/adventure-time-sux/1234/3
+>
+> To unsubscribe from these emails, visit your [user preferences](http://localhost:3000/user_preferences).
+>
diff --git a/spec/lib/gitlab/email/handler/create_note_handler_spec.rb b/spec/lib/gitlab/email/handler/create_note_handler_spec.rb
index a2119b0dadf..4909fed6b77 100644
--- a/spec/lib/gitlab/email/handler/create_note_handler_spec.rb
+++ b/spec/lib/gitlab/email/handler/create_note_handler_spec.rb
@@ -60,6 +60,67 @@ describe Gitlab::Email::Handler::CreateNoteHandler, lib: true do
     it "raises an InvalidNoteError" do
       expect { receiver.execute }.to raise_error(Gitlab::Email::InvalidNoteError)
     end
+
+    context 'because the note was commands only' do
+      let!(:email_raw) { fixture_file("emails/commands_only_reply.eml") }
+
+      context 'and current user cannot update noteable' do
+        it 'raises a CommandsOnlyNoteError' do
+          expect { receiver.execute }.to raise_error(Gitlab::Email::InvalidNoteError)
+        end
+      end
+
+      context 'and current user can update noteable' do
+        before do
+          project.team << [user, :developer]
+        end
+
+        it 'does not raise an error' do
+          expect(TodoService.new.todo_exist?(noteable, user)).to be_falsy
+
+          # One system note is created for the 'close' event
+          expect { receiver.execute }.to change { noteable.notes.count }.by(1)
+
+          expect(noteable.reload).to be_closed
+          expect(noteable.due_date).to eq(Date.tomorrow)
+          expect(TodoService.new.todo_exist?(noteable, user)).to be_truthy
+        end
+      end
+    end
+  end
+
+  context 'when the note contains slash commands' do
+    let!(:email_raw) { fixture_file("emails/commands_in_reply.eml") }
+
+    context 'and current user cannot update noteable' do
+      it 'post a note and does not update the noteable' do
+        expect(TodoService.new.todo_exist?(noteable, user)).to be_falsy
+
+        # One system note is created for the new note
+        expect { receiver.execute }.to change { noteable.notes.count }.by(1)
+
+        expect(noteable.reload).to be_open
+        expect(noteable.due_date).to be_nil
+        expect(TodoService.new.todo_exist?(noteable, user)).to be_falsy
+      end
+    end
+
+    context 'and current user can update noteable' do
+      before do
+        project.team << [user, :developer]
+      end
+
+      it 'post a note and updates the noteable' do
+        expect(TodoService.new.todo_exist?(noteable, user)).to be_falsy
+
+        # One system note is created for the new note, one for the 'close' event
+        expect { receiver.execute }.to change { noteable.notes.count }.by(2)
+
+        expect(noteable.reload).to be_closed
+        expect(noteable.due_date).to eq(Date.tomorrow)
+        expect(TodoService.new.todo_exist?(noteable, user)).to be_truthy
+      end
+    end
   end
 
   context "when the reply is blank" do
diff --git a/spec/lib/gitlab/slash_commands/command_definition_spec.rb b/spec/lib/gitlab/slash_commands/command_definition_spec.rb
new file mode 100644
index 00000000000..c9c2f314e57
--- /dev/null
+++ b/spec/lib/gitlab/slash_commands/command_definition_spec.rb
@@ -0,0 +1,173 @@
+require 'spec_helper'
+
+describe Gitlab::SlashCommands::CommandDefinition do
+  subject { described_class.new(:command) }
+
+  describe "#all_names" do
+    context "when the command has aliases" do
+      before do
+        subject.aliases = [:alias1, :alias2]
+      end
+
+      it "returns an array with the name and aliases" do
+        expect(subject.all_names).to eq([:command, :alias1, :alias2])
+      end
+    end
+
+    context "when the command doesn't have aliases" do
+      it "returns an array with the name" do
+        expect(subject.all_names).to eq([:command])
+      end
+    end
+  end
+
+  describe "#noop?" do
+    context "when the command has an action block" do
+      before do
+        subject.action_block = proc { }
+      end
+
+      it "returns false" do
+        expect(subject.noop?).to be false
+      end
+    end
+
+    context "when the command doesn't have an action block" do
+      it "returns true" do
+        expect(subject.noop?).to be true
+      end
+    end
+  end
+
+  describe "#available?" do
+    let(:opts) { { go: false } }
+
+    context "when the command has a condition block" do
+      before do
+        subject.condition_block = proc { go }
+      end
+
+      context "when the condition block returns true" do
+        before do
+          opts[:go] = true
+        end
+
+        it "returns true" do
+          expect(subject.available?(opts)).to be true
+        end
+      end
+
+      context "when the condition block returns false" do
+        it "returns false" do
+          expect(subject.available?(opts)).to be false
+        end
+      end
+    end
+
+    context "when the command doesn't have a condition block" do
+      it "returns true" do
+        expect(subject.available?(opts)).to be true
+      end
+    end
+  end
+
+  describe "#execute" do
+    let(:context) { OpenStruct.new(run: false) }
+
+    context "when the command is a noop" do
+      it "doesn't execute the command" do
+        expect(context).not_to receive(:instance_exec)
+
+        subject.execute(context, {}, nil)
+
+        expect(context.run).to be false
+      end
+    end
+
+    context "when the command is not a noop" do
+      before do
+        subject.action_block = proc { self.run = true }
+      end
+
+      context "when the command is not available" do
+        before do
+          subject.condition_block = proc { false }
+        end
+
+        it "doesn't execute the command" do
+          subject.execute(context, {}, nil)
+
+          expect(context.run).to be false
+        end
+      end
+
+      context "when the command is available" do
+        context "when the commnd has no arguments" do
+          before do
+            subject.action_block = proc { self.run = true }
+          end
+
+          context "when the command is provided an argument" do
+            it "executes the command" do
+              subject.execute(context, {}, true)
+
+              expect(context.run).to be true
+            end
+          end
+
+          context "when the command is not provided an argument" do
+            it "executes the command" do
+              subject.execute(context, {}, nil)
+
+              expect(context.run).to be true
+            end
+          end
+        end
+
+        context "when the command has 1 required argument" do
+          before do
+            subject.action_block = ->(arg) { self.run = arg }
+          end
+
+          context "when the command is provided an argument" do
+            it "executes the command" do
+              subject.execute(context, {}, true)
+
+              expect(context.run).to be true
+            end
+          end
+
+          context "when the command is not provided an argument" do
+            it "doesn't execute the command" do
+              subject.execute(context, {}, nil)
+
+              expect(context.run).to be false
+            end
+          end
+        end
+
+        context "when the command has 1 optional argument" do
+          before do
+            subject.action_block = proc { |arg = nil| self.run = arg || true }
+          end
+
+          context "when the command is provided an argument" do
+            it "executes the command" do
+              subject.execute(context, {}, true)
+
+              expect(context.run).to be true
+            end
+          end
+
+          context "when the command is not provided an argument" do
+            it "executes the command" do
+              subject.execute(context, {}, nil)
+
+              expect(context.run).to be true
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/slash_commands/dsl_spec.rb b/spec/lib/gitlab/slash_commands/dsl_spec.rb
new file mode 100644
index 00000000000..26217a0e3b2
--- /dev/null
+++ b/spec/lib/gitlab/slash_commands/dsl_spec.rb
@@ -0,0 +1,77 @@
+require 'spec_helper'
+
+describe Gitlab::SlashCommands::Dsl do
+  before :all do
+    DummyClass = Struct.new(:project) do
+      include Gitlab::SlashCommands::Dsl
+
+      desc 'A command with no args'
+      command :no_args, :none do
+        "Hello World!"
+      end
+
+      params 'The first argument'
+      command :one_arg, :once, :first do |arg1|
+        arg1
+      end
+
+      desc do
+        "A dynamic description for #{noteable.upcase}"
+      end
+      params 'The first argument', 'The second argument'
+      command :two_args do |arg1, arg2|
+        [arg1, arg2]
+      end
+
+      command :cc
+
+      condition do
+        project == 'foo'
+      end
+      command :cond_action do |arg|
+        arg
+      end
+    end
+  end
+
+  describe '.command_definitions' do
+    it 'returns an array with commands definitions' do
+      no_args_def, one_arg_def, two_args_def, cc_def, cond_action_def = DummyClass.command_definitions
+
+      expect(no_args_def.name).to eq(:no_args)
+      expect(no_args_def.aliases).to eq([:none])
+      expect(no_args_def.description).to eq('A command with no args')
+      expect(no_args_def.params).to eq([])
+      expect(no_args_def.condition_block).to be_nil
+      expect(no_args_def.action_block).to be_a_kind_of(Proc)
+
+      expect(one_arg_def.name).to eq(:one_arg)
+      expect(one_arg_def.aliases).to eq([:once, :first])
+      expect(one_arg_def.description).to eq('')
+      expect(one_arg_def.params).to eq(['The first argument'])
+      expect(one_arg_def.condition_block).to be_nil
+      expect(one_arg_def.action_block).to be_a_kind_of(Proc)
+
+      expect(two_args_def.name).to eq(:two_args)
+      expect(two_args_def.aliases).to eq([])
+      expect(two_args_def.to_h(noteable: "issue")[:description]).to eq('A dynamic description for ISSUE')
+      expect(two_args_def.params).to eq(['The first argument', 'The second argument'])
+      expect(two_args_def.condition_block).to be_nil
+      expect(two_args_def.action_block).to be_a_kind_of(Proc)
+
+      expect(cc_def.name).to eq(:cc)
+      expect(cc_def.aliases).to eq([])
+      expect(cc_def.description).to eq('')
+      expect(cc_def.params).to eq([])
+      expect(cc_def.condition_block).to be_nil
+      expect(cc_def.action_block).to be_nil
+
+      expect(cond_action_def.name).to eq(:cond_action)
+      expect(cond_action_def.aliases).to eq([])
+      expect(cond_action_def.description).to eq('')
+      expect(cond_action_def.params).to eq([])
+      expect(cond_action_def.condition_block).to be_a_kind_of(Proc)
+      expect(cond_action_def.action_block).to be_a_kind_of(Proc)
+    end
+  end
+end
diff --git a/spec/lib/gitlab/slash_commands/extractor_spec.rb b/spec/lib/gitlab/slash_commands/extractor_spec.rb
new file mode 100644
index 00000000000..1e4954c4af8
--- /dev/null
+++ b/spec/lib/gitlab/slash_commands/extractor_spec.rb
@@ -0,0 +1,215 @@
+require 'spec_helper'
+
+describe Gitlab::SlashCommands::Extractor do
+  let(:definitions) do
+    Class.new do
+      include Gitlab::SlashCommands::Dsl
+
+      command(:reopen, :open) { }
+      command(:assign) { }
+      command(:labels) { }
+      command(:power) { }
+    end.command_definitions
+  end
+
+  let(:extractor) { described_class.new(definitions) }
+
+  shared_examples 'command with no argument' do
+    it 'extracts command' do
+      msg, commands = extractor.extract_commands(original_msg)
+
+      expect(commands).to eq [['reopen']]
+      expect(msg).to eq final_msg
+    end
+  end
+
+  shared_examples 'command with a single argument' do
+    it 'extracts command' do
+      msg, commands = extractor.extract_commands(original_msg)
+
+      expect(commands).to eq [['assign', '@joe']]
+      expect(msg).to eq final_msg
+    end
+  end
+
+  shared_examples 'command with multiple arguments' do
+    it 'extracts command' do
+      msg, commands = extractor.extract_commands(original_msg)
+
+      expect(commands).to eq [['labels', '~foo ~"bar baz" label']]
+      expect(msg).to eq final_msg
+    end
+  end
+
+  describe '#extract_commands' do
+    describe 'command with no argument' do
+      context 'at the start of content' do
+        it_behaves_like 'command with no argument' do
+          let(:original_msg) { "/reopen\nworld" }
+          let(:final_msg) { "world" }
+        end
+      end
+
+      context 'in the middle of content' do
+        it_behaves_like 'command with no argument' do
+          let(:original_msg) { "hello\n/reopen\nworld" }
+          let(:final_msg) { "hello\nworld" }
+        end
+      end
+
+      context 'in the middle of a line' do
+        it 'does not extract command' do
+          msg = "hello\nworld /reopen"
+          msg, commands = extractor.extract_commands(msg)
+
+          expect(commands).to be_empty
+          expect(msg).to eq "hello\nworld /reopen"
+        end
+      end
+
+      context 'at the end of content' do
+        it_behaves_like 'command with no argument' do
+          let(:original_msg) { "hello\n/reopen" }
+          let(:final_msg) { "hello" }
+        end
+      end
+    end
+
+    describe 'command with a single argument' do
+      context 'at the start of content' do
+        it_behaves_like 'command with a single argument' do
+          let(:original_msg) { "/assign @joe\nworld" }
+          let(:final_msg) { "world" }
+        end
+      end
+
+      context 'in the middle of content' do
+        it_behaves_like 'command with a single argument' do
+          let(:original_msg) { "hello\n/assign @joe\nworld" }
+          let(:final_msg) { "hello\nworld" }
+        end
+      end
+
+      context 'in the middle of a line' do
+        it 'does not extract command' do
+          msg = "hello\nworld /assign @joe"
+          msg, commands = extractor.extract_commands(msg)
+
+          expect(commands).to be_empty
+          expect(msg).to eq "hello\nworld /assign @joe"
+        end
+      end
+
+      context 'at the end of content' do
+        it_behaves_like 'command with a single argument' do
+          let(:original_msg) { "hello\n/assign @joe" }
+          let(:final_msg) { "hello" }
+        end
+      end
+
+      context 'when argument is not separated with a space' do
+        it 'does not extract command' do
+          msg = "hello\n/assign@joe\nworld"
+          msg, commands = extractor.extract_commands(msg)
+
+          expect(commands).to be_empty
+          expect(msg).to eq "hello\n/assign@joe\nworld"
+        end
+      end
+    end
+
+    describe 'command with multiple arguments' do
+      context 'at the start of content' do
+        it_behaves_like 'command with multiple arguments' do
+          let(:original_msg) { %(/labels ~foo ~"bar baz" label\nworld) }
+          let(:final_msg) { "world" }
+        end
+      end
+
+      context 'in the middle of content' do
+        it_behaves_like 'command with multiple arguments' do
+          let(:original_msg) { %(hello\n/labels ~foo ~"bar baz" label\nworld) }
+          let(:final_msg) { "hello\nworld" }
+        end
+      end
+
+      context 'in the middle of a line' do
+        it 'does not extract command' do
+          msg = %(hello\nworld /labels ~foo ~"bar baz" label)
+          msg, commands = extractor.extract_commands(msg)
+
+          expect(commands).to be_empty
+          expect(msg).to eq %(hello\nworld /labels ~foo ~"bar baz" label)
+        end
+      end
+
+      context 'at the end of content' do
+        it_behaves_like 'command with multiple arguments' do
+          let(:original_msg) { %(hello\n/labels ~foo ~"bar baz" label) }
+          let(:final_msg) { "hello" }
+        end
+      end
+
+      context 'when argument is not separated with a space' do
+        it 'does not extract command' do
+          msg = %(hello\n/labels~foo ~"bar baz" label\nworld)
+          msg, commands = extractor.extract_commands(msg)
+
+          expect(commands).to be_empty
+          expect(msg).to eq %(hello\n/labels~foo ~"bar baz" label\nworld)
+        end
+      end
+    end
+
+    it 'extracts command with multiple arguments and various prefixes' do
+      msg = %(hello\n/power @user.name %9.10 ~"bar baz.2"\nworld)
+      msg, commands = extractor.extract_commands(msg)
+
+      expect(commands).to eq [['power', '@user.name %9.10 ~"bar baz.2"']]
+      expect(msg).to eq "hello\nworld"
+    end
+
+    it 'extracts multiple commands' do
+      msg = %(hello\n/power @user.name %9.10 ~"bar baz.2" label\nworld\n/reopen)
+      msg, commands = extractor.extract_commands(msg)
+
+      expect(commands).to eq [['power', '@user.name %9.10 ~"bar baz.2" label'], ['reopen']]
+      expect(msg).to eq "hello\nworld"
+    end
+
+    it 'does not alter original content if no command is found' do
+      msg = 'Fixes #123'
+      msg, commands = extractor.extract_commands(msg)
+
+      expect(commands).to be_empty
+      expect(msg).to eq 'Fixes #123'
+    end
+
+    it 'does not extract commands inside a blockcode' do
+      msg = "Hello\r\n```\r\nThis is some text\r\n/close\r\n/assign @user\r\n```\r\n\r\nWorld"
+      expected = msg.delete("\r")
+      msg, commands = extractor.extract_commands(msg)
+
+      expect(commands).to be_empty
+      expect(msg).to eq expected
+    end
+
+    it 'does not extract commands inside a blockquote' do
+      msg = "Hello\r\n>>>\r\nThis is some text\r\n/close\r\n/assign @user\r\n>>>\r\n\r\nWorld"
+      expected = msg.delete("\r")
+      msg, commands = extractor.extract_commands(msg)
+
+      expect(commands).to be_empty
+      expect(msg).to eq expected
+    end
+
+    it 'does not extract commands inside a HTML tag' do
+      msg = "Hello\r\n<div>\r\nThis is some text\r\n/close\r\n/assign @user\r\n</div>\r\n\r\nWorld"
+      expected = msg.delete("\r")
+      msg, commands = extractor.extract_commands(msg)
+
+      expect(commands).to be_empty
+      expect(msg).to eq expected
+    end
+  end
+end
diff --git a/spec/services/issues/close_service_spec.rb b/spec/services/issues/close_service_spec.rb
index 1318607a388..aff022a573e 100644
--- a/spec/services/issues/close_service_spec.rb
+++ b/spec/services/issues/close_service_spec.rb
@@ -3,6 +3,7 @@ require 'spec_helper'
 describe Issues::CloseService, services: true do
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
+  let(:guest) { create(:user) }
   let(:issue) { create(:issue, assignee: user2) }
   let(:project) { issue.project }
   let!(:todo) { create(:todo, :assigned, user: user, project: project, target: issue, author: user2) }
@@ -10,13 +11,14 @@ describe Issues::CloseService, services: true do
   before do
     project.team << [user, :master]
     project.team << [user2, :developer]
+    project.team << [guest, :guest]
   end
 
   describe '#execute' do
     context "valid params" do
       before do
         perform_enqueued_jobs do
-          @issue = Issues::CloseService.new(project, user, {}).execute(issue)
+          @issue = described_class.new(project, user, {}).execute(issue)
         end
       end
 
@@ -39,10 +41,22 @@ describe Issues::CloseService, services: true do
       end
     end
 
+    context 'current user is not authorized to close issue' do
+      before do
+        perform_enqueued_jobs do
+          @issue = described_class.new(project, guest).execute(issue)
+        end
+      end
+
+      it 'does not close the issue' do
+        expect(@issue).to be_open
+      end
+    end
+
     context "external issue tracker" do
       before do
         allow(project).to receive(:default_issues_tracker?).and_return(false)
-        @issue = Issues::CloseService.new(project, user, {}).execute(issue)
+        @issue = described_class.new(project, user, {}).execute(issue)
       end
 
       it { expect(@issue).to be_valid }
diff --git a/spec/services/issues/create_service_spec.rb b/spec/services/issues/create_service_spec.rb
index 1ee9f3aae4d..fcc3c0a00bd 100644
--- a/spec/services/issues/create_service_spec.rb
+++ b/spec/services/issues/create_service_spec.rb
@@ -73,5 +73,7 @@ describe Issues::CreateService, services: true do
         end
       end
     end
+
+    it_behaves_like 'new issuable record that supports slash commands'
   end
 end
diff --git a/spec/services/issues/reopen_service_spec.rb b/spec/services/issues/reopen_service_spec.rb
new file mode 100644
index 00000000000..34a89fcd4e1
--- /dev/null
+++ b/spec/services/issues/reopen_service_spec.rb
@@ -0,0 +1,25 @@
+require 'spec_helper'
+
+describe Issues::ReopenService, services: true do
+  let(:guest) { create(:user) }
+  let(:issue) { create(:issue, :closed) }
+  let(:project) { issue.project }
+
+  before do
+    project.team << [guest, :guest]
+  end
+
+  describe '#execute' do
+    context 'current user is not authorized to reopen issue' do
+      before do
+        perform_enqueued_jobs do
+          @issue = described_class.new(project, guest).execute(issue)
+        end
+      end
+
+      it 'does not reopen the issue' do
+        expect(@issue).to be_closed
+      end
+    end
+  end
+end
diff --git a/spec/services/merge_requests/close_service_spec.rb b/spec/services/merge_requests/close_service_spec.rb
index 403533be5d9..24c25e4350f 100644
--- a/spec/services/merge_requests/close_service_spec.rb
+++ b/spec/services/merge_requests/close_service_spec.rb
@@ -3,6 +3,7 @@ require 'spec_helper'
 describe MergeRequests::CloseService, services: true do
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
+  let(:guest) { create(:user) }
   let(:merge_request) { create(:merge_request, assignee: user2) }
   let(:project) { merge_request.project }
   let!(:todo) { create(:todo, :assigned, user: user, project: project, target: merge_request, author: user2) }
@@ -10,11 +11,12 @@ describe MergeRequests::CloseService, services: true do
   before do
     project.team << [user, :master]
     project.team << [user2, :developer]
+    project.team << [guest, :guest]
   end
 
   describe '#execute' do
     context 'valid params' do
-      let(:service) { MergeRequests::CloseService.new(project, user, {}) }
+      let(:service) { described_class.new(project, user, {}) }
 
       before do
         allow(service).to receive(:execute_hooks)
@@ -47,5 +49,17 @@ describe MergeRequests::CloseService, services: true do
         expect(todo.reload).to be_done
       end
     end
+
+    context 'current user is not authorized to close merge request' do
+      before do
+        perform_enqueued_jobs do
+          @merge_request = described_class.new(project, guest).execute(merge_request)
+        end
+      end
+
+      it 'does not close the merge request' do
+        expect(@merge_request).to be_open
+      end
+    end
   end
 end
diff --git a/spec/services/merge_requests/create_service_spec.rb b/spec/services/merge_requests/create_service_spec.rb
index b84a580967a..c1e4f8bd96b 100644
--- a/spec/services/merge_requests/create_service_spec.rb
+++ b/spec/services/merge_requests/create_service_spec.rb
@@ -17,7 +17,7 @@ describe MergeRequests::CreateService, services: true do
         }
       end
 
-      let(:service) { MergeRequests::CreateService.new(project, user, opts) }
+      let(:service) { described_class.new(project, user, opts) }
 
       before do
         project.team << [user, :master]
@@ -74,5 +74,14 @@ describe MergeRequests::CreateService, services: true do
         end
       end
     end
+
+    it_behaves_like 'new issuable record that supports slash commands' do
+      let(:default_params) do
+        {
+          source_branch: 'feature',
+          target_branch: 'master'
+        }
+      end
+    end
   end
 end
diff --git a/spec/services/merge_requests/reopen_service_spec.rb b/spec/services/merge_requests/reopen_service_spec.rb
index 3419b8bf5e6..af7424a76a9 100644
--- a/spec/services/merge_requests/reopen_service_spec.rb
+++ b/spec/services/merge_requests/reopen_service_spec.rb
@@ -3,22 +3,23 @@ require 'spec_helper'
 describe MergeRequests::ReopenService, services: true do
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
-  let(:merge_request) { create(:merge_request, assignee: user2) }
+  let(:guest) { create(:user) }
+  let(:merge_request) { create(:merge_request, :closed, assignee: user2) }
   let(:project) { merge_request.project }
 
   before do
     project.team << [user, :master]
     project.team << [user2, :developer]
+    project.team << [guest, :guest]
   end
 
   describe '#execute' do
     context 'valid params' do
-      let(:service) { MergeRequests::ReopenService.new(project, user, {}) }
+      let(:service) { described_class.new(project, user, {}) }
 
       before do
         allow(service).to receive(:execute_hooks)
 
-        merge_request.state = :closed
         perform_enqueued_jobs do
           service.execute(merge_request)
         end
@@ -43,5 +44,17 @@ describe MergeRequests::ReopenService, services: true do
         expect(note.note).to include 'Status changed to reopened'
       end
     end
+
+    context 'current user is not authorized to reopen merge request' do
+      before do
+        perform_enqueued_jobs do
+          @merge_request = described_class.new(project, guest).execute(merge_request)
+        end
+      end
+
+      it 'does not reopen the merge request' do
+        expect(@merge_request).to be_closed
+      end
+    end
   end
 end
diff --git a/spec/services/notes/create_service_spec.rb b/spec/services/notes/create_service_spec.rb
index 32753e84b31..93885c84dc3 100644
--- a/spec/services/notes/create_service_spec.rb
+++ b/spec/services/notes/create_service_spec.rb
@@ -4,22 +4,36 @@ describe Notes::CreateService, services: true do
   let(:project) { create(:empty_project) }
   let(:issue) { create(:issue, project: project) }
   let(:user) { create(:user) }
+  let(:opts) do
+    { note: 'Awesome comment', noteable_type: 'Issue', noteable_id: issue.id }
+  end
 
   describe '#execute' do
+    before do
+      project.team << [user, :master]
+    end
+
     context "valid params" do
       before do
-        project.team << [user, :master]
-        opts = {
-          note: 'Awesome comment',
-          noteable_type: 'Issue',
-          noteable_id: issue.id
-        }
-
         @note = Notes::CreateService.new(project, user, opts).execute
       end
 
       it { expect(@note).to be_valid }
-      it { expect(@note.note).to eq('Awesome comment') }
+      it { expect(@note.note).to eq(opts[:note]) }
+    end
+
+    describe 'note with commands' do
+      describe '/close, /label, /assign & /milestone' do
+        let(:note_text) { %(HELLO\n/close\n/assign @#{user.username}\nWORLD) }
+
+        it 'saves the note and does not alter the note text' do
+          expect_any_instance_of(Issues::UpdateService).to receive(:execute).and_call_original
+
+          note = described_class.new(project, user, opts.merge(note: note_text)).execute
+
+          expect(note.note).to eq "HELLO\nWORLD"
+        end
+      end
     end
   end
 
@@ -42,7 +56,7 @@ describe Notes::CreateService, services: true do
 
     it "creates regular note if emoji name is invalid" do
       opts = {
-        note: ':smile: moretext: ',
+        note: ':smile: moretext:',
         noteable_type: 'Issue',
         noteable_id: issue.id
       }
diff --git a/spec/services/notes/slash_commands_service_spec.rb b/spec/services/notes/slash_commands_service_spec.rb
new file mode 100644
index 00000000000..4f231aab161
--- /dev/null
+++ b/spec/services/notes/slash_commands_service_spec.rb
@@ -0,0 +1,140 @@
+require 'spec_helper'
+
+describe Notes::SlashCommandsService, services: true do
+  shared_context 'note on noteable' do
+    let(:project) { create(:empty_project) }
+    let(:master) { create(:user).tap { |u| project.team << [u, :master] } }
+    let(:assignee) { create(:user) }
+  end
+
+  shared_examples 'note on noteable that does not support slash commands' do
+    include_context 'note on noteable'
+
+    before do
+      note.note = note_text
+    end
+
+    describe 'note with only command' do
+      describe '/close, /label, /assign & /milestone' do
+        let(:note_text) { %(/close\n/assign @#{assignee.username}") }
+
+        it 'saves the note and does not alter the note text' do
+          content, command_params = service.extract_commands(note)
+
+          expect(content).to eq note_text
+          expect(command_params).to be_empty
+        end
+      end
+    end
+
+    describe 'note with command & text' do
+      describe '/close, /label, /assign & /milestone' do
+        let(:note_text) { %(HELLO\n/close\n/assign @#{assignee.username}\nWORLD) }
+
+        it 'saves the note and does not alter the note text' do
+          content, command_params = service.extract_commands(note)
+
+          expect(content).to eq note_text
+          expect(command_params).to be_empty
+        end
+      end
+    end
+  end
+
+  shared_examples 'note on noteable that supports slash commands' do
+    include_context 'note on noteable'
+
+    before do
+      note.note = note_text
+    end
+
+    let!(:milestone) { create(:milestone, project: project) }
+    let!(:labels) { create_pair(:label, project: project) }
+
+    describe 'note with only command' do
+      describe '/close, /label, /assign & /milestone' do
+        let(:note_text) do
+          %(/close\n/label ~#{labels.first.name} ~#{labels.last.name}\n/assign @#{assignee.username}\n/milestone %"#{milestone.name}")
+        end
+
+        it 'closes noteable, sets labels, assigns, and sets milestone to noteable, and leave no note' do
+          content, command_params = service.extract_commands(note)
+          service.execute(command_params, note)
+
+          expect(content).to eq ''
+          expect(note.noteable).to be_closed
+          expect(note.noteable.labels).to match_array(labels)
+          expect(note.noteable.assignee).to eq(assignee)
+          expect(note.noteable.milestone).to eq(milestone)
+        end
+      end
+
+      describe '/reopen' do
+        before do
+          note.noteable.close!
+          expect(note.noteable).to be_closed
+        end
+        let(:note_text) { '/reopen' }
+
+        it 'opens the noteable, and leave no note' do
+          content, command_params = service.extract_commands(note)
+          service.execute(command_params, note)
+
+          expect(content).to eq ''
+          expect(note.noteable).to be_open
+        end
+      end
+    end
+
+    describe 'note with command & text' do
+      describe '/close, /label, /assign & /milestone' do
+        let(:note_text) do
+          %(HELLO\n/close\n/label ~#{labels.first.name} ~#{labels.last.name}\n/assign @#{assignee.username}\n/milestone %"#{milestone.name}"\nWORLD)
+        end
+
+        it 'closes noteable, sets labels, assigns, and sets milestone to noteable' do
+          content, command_params = service.extract_commands(note)
+          service.execute(command_params, note)
+
+          expect(content).to eq "HELLO\nWORLD"
+          expect(note.noteable).to be_closed
+          expect(note.noteable.labels).to match_array(labels)
+          expect(note.noteable.assignee).to eq(assignee)
+          expect(note.noteable.milestone).to eq(milestone)
+        end
+      end
+
+      describe '/reopen' do
+        before do
+          note.noteable.close
+          expect(note.noteable).to be_closed
+        end
+        let(:note_text) { "HELLO\n/reopen\nWORLD" }
+
+        it 'opens the noteable' do
+          content, command_params = service.extract_commands(note)
+          service.execute(command_params, note)
+
+          expect(content).to eq "HELLO\nWORLD"
+          expect(note.noteable).to be_open
+        end
+      end
+    end
+  end
+
+  describe '#execute' do
+    let(:service) { described_class.new(project, master) }
+
+    it_behaves_like 'note on noteable that supports slash commands' do
+      let(:note) { build(:note_on_issue, project: project) }
+    end
+
+    it_behaves_like 'note on noteable that supports slash commands' do
+      let(:note) { build(:note_on_merge_request, project: project) }
+    end
+
+    it_behaves_like 'note on noteable that does not support slash commands' do
+      let(:note) { build(:note_on_commit, project: project) }
+    end
+  end
+end
diff --git a/spec/services/slash_commands/interpret_service_spec.rb b/spec/services/slash_commands/interpret_service_spec.rb
new file mode 100644
index 00000000000..a616275e883
--- /dev/null
+++ b/spec/services/slash_commands/interpret_service_spec.rb
@@ -0,0 +1,384 @@
+require 'spec_helper'
+
+describe SlashCommands::InterpretService, services: true do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:issue) { create(:issue, project: project) }
+  let(:milestone) { create(:milestone, project: project, title: '9.10') }
+  let(:inprogress) { create(:label, project: project, title: 'In Progress') }
+  let(:bug) { create(:label, project: project, title: 'Bug') }
+
+  before do
+    project.team << [user, :developer]
+  end
+
+  describe '#execute' do
+    let(:service) { described_class.new(project, user) }
+    let(:merge_request) { create(:merge_request, source_project: project) }
+
+    shared_examples 'reopen command' do
+      it 'returns state_event: "reopen" if content contains /reopen' do
+        issuable.close!
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(state_event: 'reopen')
+      end
+    end
+
+    shared_examples 'close command' do
+      it 'returns state_event: "close" if content contains /close' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(state_event: 'close')
+      end
+    end
+
+    shared_examples 'title command' do
+      it 'populates title: "A brand new title" if content contains /title A brand new title' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(title: 'A brand new title')
+      end
+    end
+
+    shared_examples 'assign command' do
+      it 'fetches assignee and populates assignee_id if content contains /assign' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(assignee_id: user.id)
+      end
+    end
+
+    shared_examples 'unassign command' do
+      it 'populates assignee_id: nil if content contains /unassign' do
+        issuable.update(assignee_id: user.id)
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(assignee_id: nil)
+      end
+    end
+
+    shared_examples 'milestone command' do
+      it 'fetches milestone and populates milestone_id if content contains /milestone' do
+        milestone # populate the milestone
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(milestone_id: milestone.id)
+      end
+    end
+
+    shared_examples 'remove_milestone command' do
+      it 'populates milestone_id: nil if content contains /remove_milestone' do
+        issuable.update(milestone_id: milestone.id)
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(milestone_id: nil)
+      end
+    end
+
+    shared_examples 'label command' do
+      it 'fetches label ids and populates add_label_ids if content contains /label' do
+        bug # populate the label
+        inprogress # populate the label
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(add_label_ids: [bug.id, inprogress.id])
+      end
+    end
+
+    shared_examples 'unlabel command' do
+      it 'fetches label ids and populates remove_label_ids if content contains /unlabel' do
+        issuable.update(label_ids: [inprogress.id]) # populate the label
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(remove_label_ids: [inprogress.id])
+      end
+    end
+
+    shared_examples 'unlabel command with no argument' do
+      it 'populates label_ids: [] if content contains /unlabel with no arguments' do
+        issuable.update(label_ids: [inprogress.id]) # populate the label
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(label_ids: [])
+      end
+    end
+
+    shared_examples 'relabel command' do
+      it 'populates label_ids: [] if content contains /relabel' do
+        issuable.update(label_ids: [bug.id]) # populate the label
+        inprogress # populate the label
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(label_ids: [inprogress.id])
+      end
+    end
+
+    shared_examples 'todo command' do
+      it 'populates todo_event: "add" if content contains /todo' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(todo_event: 'add')
+      end
+    end
+
+    shared_examples 'done command' do
+      it 'populates todo_event: "done" if content contains /done' do
+        TodoService.new.mark_todo(issuable, user)
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(todo_event: 'done')
+      end
+    end
+
+    shared_examples 'subscribe command' do
+      it 'populates subscription_event: "subscribe" if content contains /subscribe' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(subscription_event: 'subscribe')
+      end
+    end
+
+    shared_examples 'unsubscribe command' do
+      it 'populates subscription_event: "unsubscribe" if content contains /unsubscribe' do
+        issuable.subscribe(user)
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(subscription_event: 'unsubscribe')
+      end
+    end
+
+    shared_examples 'due command' do
+      it 'populates due_date: Date.new(2016, 8, 28) if content contains /due 2016-08-28' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(due_date: defined?(expected_date) ? expected_date : Date.new(2016, 8, 28))
+      end
+    end
+
+    shared_examples 'remove_due_date command' do
+      it 'populates due_date: nil if content contains /remove_due_date' do
+        issuable.update(due_date: Date.today)
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(due_date: nil)
+      end
+    end
+
+    shared_examples 'empty command' do
+      it 'populates {} if content contains an unsupported command' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to be_empty
+      end
+    end
+
+    it_behaves_like 'reopen command' do
+      let(:content) { '/reopen' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'reopen command' do
+      let(:content) { '/reopen' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'close command' do
+      let(:content) { '/close' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'close command' do
+      let(:content) { '/close' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'title command' do
+      let(:content) { '/title A brand new title' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'title command' do
+      let(:content) { '/title A brand new title' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'empty command' do
+      let(:content) { '/title' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'assign command' do
+      let(:content) { "/assign @#{user.username}" }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'assign command' do
+      let(:content) { "/assign @#{user.username}" }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'empty command' do
+      let(:content) { '/assign @abcd1234' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'empty command' do
+      let(:content) { '/assign' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'unassign command' do
+      let(:content) { '/unassign' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'unassign command' do
+      let(:content) { '/unassign' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'milestone command' do
+      let(:content) { "/milestone %#{milestone.title}" }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'milestone command' do
+      let(:content) { "/milestone %#{milestone.title}" }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'remove_milestone command' do
+      let(:content) { '/remove_milestone' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'remove_milestone command' do
+      let(:content) { '/remove_milestone' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'label command' do
+      let(:content) { %(/label ~"#{inprogress.title}" ~#{bug.title} ~unknown) }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'label command' do
+      let(:content) { %(/label ~"#{inprogress.title}" ~#{bug.title} ~unknown) }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'unlabel command' do
+      let(:content) { %(/unlabel ~"#{inprogress.title}") }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'unlabel command' do
+      let(:content) { %(/unlabel ~"#{inprogress.title}") }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'unlabel command with no argument' do
+      let(:content) { %(/unlabel) }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'unlabel command with no argument' do
+      let(:content) { %(/unlabel) }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'relabel command' do
+      let(:content) { %(/relabel ~"#{inprogress.title}") }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'relabel command' do
+      let(:content) { %(/relabel ~"#{inprogress.title}") }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'todo command' do
+      let(:content) { '/todo' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'todo command' do
+      let(:content) { '/todo' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'done command' do
+      let(:content) { '/done' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'done command' do
+      let(:content) { '/done' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'subscribe command' do
+      let(:content) { '/subscribe' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'subscribe command' do
+      let(:content) { '/subscribe' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'unsubscribe command' do
+      let(:content) { '/unsubscribe' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'unsubscribe command' do
+      let(:content) { '/unsubscribe' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'due command' do
+      let(:content) { '/due 2016-08-28' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'due command' do
+      let(:content) { '/due tomorrow' }
+      let(:issuable) { issue }
+      let(:expected_date) { Date.tomorrow }
+    end
+
+    it_behaves_like 'due command' do
+      let(:content) { '/due 5 days from now' }
+      let(:issuable) { issue }
+      let(:expected_date) { 5.days.from_now.to_date }
+    end
+
+    it_behaves_like 'due command' do
+      let(:content) { '/due in 2 days' }
+      let(:issuable) { issue }
+      let(:expected_date) { 2.days.from_now.to_date }
+    end
+
+    it_behaves_like 'empty command' do
+      let(:content) { '/due foo bar' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'empty command' do
+      let(:content) { '/due 2016-08-28' }
+      let(:issuable) { merge_request }
+    end
+
+    it_behaves_like 'remove_due_date command' do
+      let(:content) { '/remove_due_date' }
+      let(:issuable) { issue }
+    end
+
+    it_behaves_like 'empty command' do
+      let(:content) { '/remove_due_date' }
+      let(:issuable) { merge_request }
+    end
+  end
+end
diff --git a/spec/services/todo_service_spec.rb b/spec/services/todo_service_spec.rb
index a2a1d5e6d30..296fd1bd5a4 100644
--- a/spec/services/todo_service_spec.rb
+++ b/spec/services/todo_service_spec.rb
@@ -300,6 +300,18 @@ describe TodoService, services: true do
         should_create_todo(user: author, target: unassigned_issue, action: Todo::MARKED)
       end
     end
+
+    describe '#todo_exists?' do
+      it 'returns false when no todo exist for the given issuable' do
+        expect(service.todo_exist?(unassigned_issue, author)).to be_falsy
+      end
+
+      it 'returns true when a todo exist for the given issuable' do
+        service.mark_todo(unassigned_issue, author)
+
+        expect(service.todo_exist?(unassigned_issue, author)).to be_truthy
+      end
+    end
   end
 
   describe 'Merge Requests' do
diff --git a/spec/support/issuable_create_service_slash_commands_shared_examples.rb b/spec/support/issuable_create_service_slash_commands_shared_examples.rb
new file mode 100644
index 00000000000..5f9645ed44f
--- /dev/null
+++ b/spec/support/issuable_create_service_slash_commands_shared_examples.rb
@@ -0,0 +1,83 @@
+# Specifications for behavior common to all objects with executable attributes.
+# It can take a `default_params`.
+
+shared_examples 'new issuable record that supports slash commands' do
+  let!(:project) { create(:project) }
+  let(:user) { create(:user).tap { |u| project.team << [u, :master] } }
+  let(:assignee) { create(:user) }
+  let!(:milestone) { create(:milestone, project: project) }
+  let!(:labels) { create_list(:label, 3, project: project) }
+  let(:base_params) { { title: FFaker::Lorem.sentence(3) } }
+  let(:params) { base_params.merge(defined?(default_params) ? default_params : {}).merge(example_params) }
+  let(:issuable) { described_class.new(project, user, params).execute }
+
+  context 'with labels in command only' do
+    let(:example_params) do
+      {
+        description: "/label ~#{labels.first.name} ~#{labels.second.name}\n/unlabel ~#{labels.third.name}"
+      }
+    end
+
+    it 'attaches labels to issuable' do
+      expect(issuable).to be_persisted
+      expect(issuable.label_ids).to match_array([labels.first.id, labels.second.id])
+    end
+  end
+
+  context 'with labels in params and command' do
+    let(:example_params) do
+      {
+        label_ids: [labels.second.id],
+        description: "/label ~#{labels.first.name}\n/unlabel ~#{labels.third.name}"
+      }
+    end
+
+    it 'attaches all labels to issuable' do
+      expect(issuable).to be_persisted
+      expect(issuable.label_ids).to match_array([labels.first.id, labels.second.id])
+    end
+  end
+
+  context 'with assignee and milestone in command only' do
+    let(:example_params) do
+      {
+        description: %(/assign @#{assignee.username}\n/milestone %"#{milestone.name}")
+      }
+    end
+
+    it 'assigns and sets milestone to issuable' do
+      expect(issuable).to be_persisted
+      expect(issuable.assignee).to eq(assignee)
+      expect(issuable.milestone).to eq(milestone)
+    end
+  end
+
+  context 'with assignee and milestone in params and command' do
+    let(:example_params) do
+      {
+        assignee: build_stubbed(:user),
+        milestone_id: double(:milestone),
+        description: %(/assign @#{assignee.username}\n/milestone %"#{milestone.name}")
+      }
+    end
+
+    it 'assigns and sets milestone to issuable from command' do
+      expect(issuable).to be_persisted
+      expect(issuable.assignee).to eq(assignee)
+      expect(issuable.milestone).to eq(milestone)
+    end
+  end
+
+  describe '/close' do
+    let(:example_params) do
+      {
+        description: '/close'
+      }
+    end
+
+    it 'returns an open issue' do
+      expect(issuable).to be_persisted
+      expect(issuable).to be_open
+    end
+  end
+end
diff --git a/spec/support/issuable_slash_commands_shared_examples.rb b/spec/support/issuable_slash_commands_shared_examples.rb
new file mode 100644
index 00000000000..d2a49ea5c5e
--- /dev/null
+++ b/spec/support/issuable_slash_commands_shared_examples.rb
@@ -0,0 +1,289 @@
+# Specifications for behavior common to all objects with executable attributes.
+# It takes a `issuable_type`, and expect an `issuable`.
+
+shared_examples 'issuable record that supports slash commands in its description and notes' do |issuable_type|
+  let(:master) { create(:user) }
+  let(:assignee) { create(:user, username: 'bob') }
+  let(:guest) { create(:user) }
+  let(:project) { create(:project, :public) }
+  let!(:milestone) { create(:milestone, project: project, title: 'ASAP') }
+  let!(:label_bug) { create(:label, project: project, title: 'bug') }
+  let!(:label_feature) { create(:label, project: project, title: 'feature') }
+  let(:new_url_opts) { {} }
+
+  before do
+    project.team << [master, :master]
+    project.team << [assignee, :developer]
+    project.team << [guest, :guest]
+    login_with(master)
+  end
+
+  describe "new #{issuable_type}" do
+    context 'with commands in the description' do
+      it "creates the #{issuable_type} and interpret commands accordingly" do
+        visit public_send("new_namespace_project_#{issuable_type}_path", project.namespace, project, new_url_opts)
+        fill_in "#{issuable_type}_title", with: 'bug 345'
+        fill_in "#{issuable_type}_description", with: "bug description\n/label ~bug\n/milestone %\"ASAP\""
+        click_button "Submit #{issuable_type}".humanize
+
+        issuable = project.public_send(issuable_type.to_s.pluralize).first
+
+        expect(issuable.description).to eq "bug description"
+        expect(issuable.labels).to eq [label_bug]
+        expect(issuable.milestone).to eq milestone
+        expect(page).to have_content 'bug 345'
+        expect(page).to have_content 'bug description'
+      end
+    end
+  end
+
+  describe "note on #{issuable_type}" do
+    before do
+      visit public_send("namespace_project_#{issuable_type}_path", project.namespace, project, issuable)
+    end
+
+    context 'with a note containing commands' do
+      it 'creates a note without the commands and interpret the commands accordingly' do
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "Awesome!\n/assign @bob\n/label ~bug\n/milestone %\"ASAP\""
+          click_button 'Comment'
+        end
+
+        expect(page).to have_content 'Awesome!'
+        expect(page).not_to have_content '/assign @bob'
+        expect(page).not_to have_content '/label ~bug'
+        expect(page).not_to have_content '/milestone %"ASAP"'
+
+        issuable.reload
+        note = issuable.notes.user.first
+
+        expect(note.note).to eq "Awesome!"
+        expect(issuable.assignee).to eq assignee
+        expect(issuable.labels).to eq [label_bug]
+        expect(issuable.milestone).to eq milestone
+      end
+    end
+
+    context 'with a note containing only commands' do
+      it 'does not create a note but interpret the commands accordingly' do
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "/assign @bob\n/label ~bug\n/milestone %\"ASAP\""
+          click_button 'Comment'
+        end
+
+        expect(page).not_to have_content '/assign @bob'
+        expect(page).not_to have_content '/label ~bug'
+        expect(page).not_to have_content '/milestone %"ASAP"'
+        expect(page).to have_content 'Your commands have been executed!'
+
+        issuable.reload
+
+        expect(issuable.notes.user).to be_empty
+        expect(issuable.assignee).to eq assignee
+        expect(issuable.labels).to eq [label_bug]
+        expect(issuable.milestone).to eq milestone
+      end
+    end
+
+    context "with a note closing the #{issuable_type}" do
+      before do
+        expect(issuable).to be_open
+      end
+
+      context "when current user can close #{issuable_type}" do
+        it "closes the #{issuable_type}" do
+          page.within('.js-main-target-form') do
+            fill_in 'note[note]', with: "/close"
+            click_button 'Comment'
+          end
+
+          expect(page).not_to have_content '/close'
+          expect(page).to have_content 'Your commands have been executed!'
+
+          expect(issuable.reload).to be_closed
+        end
+      end
+
+      context "when current user cannot close #{issuable_type}" do
+        before do
+          logout
+          login_with(guest)
+          visit public_send("namespace_project_#{issuable_type}_path", project.namespace, project, issuable)
+        end
+
+        it "does not close the #{issuable_type}" do
+          page.within('.js-main-target-form') do
+            fill_in 'note[note]', with: "/close"
+            click_button 'Comment'
+          end
+
+          expect(page).not_to have_content '/close'
+          expect(page).not_to have_content 'Your commands have been executed!'
+
+          expect(issuable).to be_open
+        end
+      end
+    end
+
+    context "with a note reopening the #{issuable_type}" do
+      before do
+        issuable.close
+        expect(issuable).to be_closed
+      end
+
+      context "when current user can reopen #{issuable_type}" do
+        it "reopens the #{issuable_type}" do
+          page.within('.js-main-target-form') do
+            fill_in 'note[note]', with: "/reopen"
+            click_button 'Comment'
+          end
+
+          expect(page).not_to have_content '/reopen'
+          expect(page).to have_content 'Your commands have been executed!'
+
+          expect(issuable.reload).to be_open
+        end
+      end
+
+      context "when current user cannot reopen #{issuable_type}" do
+        before do
+          logout
+          login_with(guest)
+          visit public_send("namespace_project_#{issuable_type}_path", project.namespace, project, issuable)
+        end
+
+        it "does not reopen the #{issuable_type}" do
+          page.within('.js-main-target-form') do
+            fill_in 'note[note]', with: "/reopen"
+            click_button 'Comment'
+          end
+
+          expect(page).not_to have_content '/reopen'
+          expect(page).not_to have_content 'Your commands have been executed!'
+
+          expect(issuable).to be_closed
+        end
+      end
+    end
+
+    context "with a note changing the #{issuable_type}'s title" do
+      context "when current user can change title of #{issuable_type}" do
+        it "reopens the #{issuable_type}" do
+          page.within('.js-main-target-form') do
+            fill_in 'note[note]', with: "/title Awesome new title"
+            click_button 'Comment'
+          end
+
+          expect(page).not_to have_content '/title'
+          expect(page).to have_content 'Your commands have been executed!'
+
+          expect(issuable.reload.title).to eq 'Awesome new title'
+        end
+      end
+
+      context "when current user cannot change title of #{issuable_type}" do
+        before do
+          logout
+          login_with(guest)
+          visit public_send("namespace_project_#{issuable_type}_path", project.namespace, project, issuable)
+        end
+
+        it "does not reopen the #{issuable_type}" do
+          page.within('.js-main-target-form') do
+            fill_in 'note[note]', with: "/title Awesome new title"
+            click_button 'Comment'
+          end
+
+          expect(page).not_to have_content '/title'
+          expect(page).not_to have_content 'Your commands have been executed!'
+
+          expect(issuable.reload.title).not_to eq 'Awesome new title'
+        end
+      end
+    end
+
+    context "with a note marking the #{issuable_type} as todo" do
+      it "creates a new todo for the #{issuable_type}" do
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "/todo"
+          click_button 'Comment'
+        end
+
+        expect(page).not_to have_content '/todo'
+        expect(page).to have_content 'Your commands have been executed!'
+
+        todos = TodosFinder.new(master).execute
+        todo = todos.first
+
+        expect(todos.size).to eq 1
+        expect(todo).to be_pending
+        expect(todo.target).to eq issuable
+        expect(todo.author).to eq master
+        expect(todo.user).to eq master
+      end
+    end
+
+    context "with a note marking the #{issuable_type} as done" do
+      before do
+        TodoService.new.mark_todo(issuable, master)
+      end
+
+      it "creates a new todo for the #{issuable_type}" do
+        todos = TodosFinder.new(master).execute
+        todo = todos.first
+
+        expect(todos.size).to eq 1
+        expect(todos.first).to be_pending
+        expect(todo.target).to eq issuable
+        expect(todo.author).to eq master
+        expect(todo.user).to eq master
+
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "/done"
+          click_button 'Comment'
+        end
+
+        expect(page).not_to have_content '/done'
+        expect(page).to have_content 'Your commands have been executed!'
+
+        expect(todo.reload).to be_done
+      end
+    end
+
+    context "with a note subscribing to the #{issuable_type}" do
+      it "creates a new todo for the #{issuable_type}" do
+        expect(issuable.subscribed?(master)).to be_falsy
+
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "/subscribe"
+          click_button 'Comment'
+        end
+
+        expect(page).not_to have_content '/subscribe'
+        expect(page).to have_content 'Your commands have been executed!'
+
+        expect(issuable.subscribed?(master)).to be_truthy
+      end
+    end
+
+    context "with a note unsubscribing to the #{issuable_type} as done" do
+      before do
+        issuable.subscribe(master)
+      end
+
+      it "creates a new todo for the #{issuable_type}" do
+        expect(issuable.subscribed?(master)).to be_truthy
+
+        page.within('.js-main-target-form') do
+          fill_in 'note[note]', with: "/unsubscribe"
+          click_button 'Comment'
+        end
+
+        expect(page).not_to have_content '/unsubscribe'
+        expect(page).to have_content 'Your commands have been executed!'
+
+        expect(issuable.subscribed?(master)).to be_falsy
+      end
+    end
+  end
+end