Merge branch 'feature/issue-move' into 'master'

Ability to move issue to another project

Tasks:

- [x] Create scaffold of service that will move issue to another project.
- [x] Close old issue, add system note about moving issue to a new project.
- [x] Create a new issue, add system note about issue being moved from old project.
- [x] Check if issue can be moved to another project before executing service
- [x] Check permissions when moving an issue (`:admin_issue` ability)
- [x] Display select box for a new project when editing an issue
- [x] Show only projects that issue can be moved into in that select box
- [x] Add project select handler, helper and some permission filters to it
- [x] Preserve as much information as possible, including author
- [x] Prepare mechanisms that unfolds local references in issue description
- [x] Rewrite issue description with references unfolding and add some specs for it
- [x] Rewrite all system notes and comments attached to issue that is being moved
- [x] Update `Label` so that is was able to create cross reference labels (separate MR)
- [x] Add notifications about moving issue to another project
- [x] Display confirmation alert/message when issue move has been requested
- [x] Make it possible to undo selecting project where issue will be moved to
- [x] Add column to issue, that will indicate if it has been moved to another project
- [x] Do not allow to move issue that has been already moved
- [x] Write top-to-bottom feature spec in RSpec instead of Spinach

UI:

![issue_move_ui](/uploads/b3c6b563362c1fded9082cc0f51e5a74/issue_move_ui.png)

![issue_move_tooltip](/uploads/2ab913b06f52df1cafde9abe89bd9cb8/issue_move_tooltip.png)

Closes #3024

See merge request !2831

30 files changed, 866 insertions, 15 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 7abdf014c2a..7109c63ace2 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.6.0 (unreleased)
+  - Add ability to move issue to another project
   - Fix bug where wrong commit ID was being used in a merge request diff to show old image (Stan Hu)
   - Make HTTP(s) label consistent on clone bar (Stan Hu)
   - Add confidential issues
diff --git a/app/assets/javascripts/issuable_form.js.coffee b/app/assets/javascripts/issuable_form.js.coffee
index 6c1699c178c..7a788f761b7 100644
--- a/app/assets/javascripts/issuable_form.js.coffee
+++ b/app/assets/javascripts/issuable_form.js.coffee
@@ -1,5 +1,7 @@
 class @IssuableForm
+  issueMoveConfirmMsg: 'Are you sure you want to move this issue to another project?'
   wipRegex: /^\s*(\[WIP\]\s*|WIP:\s*|WIP\s+)+\s*/i
+
   constructor: (@form) ->
     GitLab.GfmAutoComplete.setup()
     new UsersSelect()
@@ -7,12 +9,13 @@ class @IssuableForm
 
     @titleField       = @form.find("input[name*='[title]']")
     @descriptionField = @form.find("textarea[name*='[description]']")
+    @issueMoveField   = @form.find("#move_to_project_id")
 
     return unless @titleField.length && @descriptionField.length
 
     @initAutosave()
 
-    @form.on "submit", @resetAutosave
+    @form.on "submit", @handleSubmit
     @form.on "click", ".btn-cancel", @resetAutosave
 
     @initWip()
@@ -30,6 +33,12 @@ class @IssuableForm
       "description"
     ]
 
+  handleSubmit: =>
+    if (parseInt(@issueMoveField?.val()) ? 0) > 0
+      return false unless confirm(@issueMoveConfirmMsg)
+
+    @resetAutosave()
+
   resetAutosave: =>
     @titleField.data("autosave").reset()
     @descriptionField.data("autosave").reset()
diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index fb8375116c6..a3c28a82d26 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -90,6 +90,12 @@ class Projects::IssuesController < Projects::ApplicationController
   def update
     @issue = Issues::UpdateService.new(project, current_user, issue_params).execute(issue)
 
+    if params[:move_to_project_id].to_i > 0
+      new_project = Project.find(params[:move_to_project_id])
+      move_service = Issues::MoveService.new(project, current_user)
+      @issue = move_service.execute(@issue, new_project)
+    end
+
     respond_to do |format|
       format.js
       format.html do
diff --git a/app/helpers/issues_helper.rb b/app/helpers/issues_helper.rb
index e00d3204027..24b90fef4fe 100644
--- a/app/helpers/issues_helper.rb
+++ b/app/helpers/issues_helper.rb
@@ -57,6 +57,19 @@ module IssuesHelper
     options_from_collection_for_select(milestones, 'id', 'title', object.milestone_id)
   end
 
+  def project_options(issuable, current_user, ability: :read_project)
+    projects = current_user.authorized_projects
+    projects = projects.select do |project|
+      current_user.can?(ability, project)
+    end
+
+    no_project = OpenStruct.new(id: 0, name_with_namespace: 'No project')
+    projects.unshift(no_project)
+    projects.delete(issuable.project)
+
+    options_from_collection_for_select(projects, :id, :name_with_namespace)
+  end
+
   def status_box_class(item)
     if item.respond_to?(:expired?) && item.expired?
       'status-box-expired'
diff --git a/app/mailers/emails/issues.rb b/app/mailers/emails/issues.rb
index 5f9adb32e00..6f54c42146c 100644
--- a/app/mailers/emails/issues.rb
+++ b/app/mailers/emails/issues.rb
@@ -36,6 +36,14 @@ module Emails
       mail_answer_thread(@issue, issue_thread_options(updated_by_user_id, recipient_id))
     end
 
+    def issue_moved_email(recipient, issue, new_issue, updated_by_user)
+      setup_issue_mail(issue.id, recipient.id)
+
+      @new_issue = new_issue
+      @new_project = new_issue.project
+      mail_answer_thread(issue, issue_thread_options(updated_by_user.id, recipient.id))
+    end
+
     private
 
     def setup_issue_mail(issue_id, recipient_id)
diff --git a/app/models/concerns/issuable.rb b/app/models/concerns/issuable.rb
index 86ab84615ba..9ab72652190 100644
--- a/app/models/concerns/issuable.rb
+++ b/app/models/concerns/issuable.rb
@@ -209,4 +209,13 @@ module Issuable
     Taskable.get_updated_tasks(old_content: previous_changes['description'].first,
                                new_content: description)
   end
+
+  ##
+  # Method that checks if issuable can be moved to another project.
+  #
+  # Should be overridden if issuable can be moved.
+  #
+  def can_move?(*)
+    false
+  end
 end
diff --git a/app/models/issue.rb b/app/models/issue.rb
index 5347d4fa1be..35e08fa915b 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -16,6 +16,7 @@
 #  state         :string(255)
 #  iid           :integer
 #  updated_by_id :integer
+#  moved_to_id   :integer
 #
 
 require 'carrierwave/orm/activerecord'
@@ -31,6 +32,8 @@ class Issue < ActiveRecord::Base
   ActsAsTaggableOn.strict_case_match = true
 
   belongs_to :project
+  belongs_to :moved_to, class_name: 'Issue'
+
   validates :project, presence: true
 
   scope :of_group,
@@ -137,6 +140,18 @@ class Issue < ActiveRecord::Base
     end.uniq.select { |mr| mr.open? && mr.closes_issue?(self) }
   end
 
+  def moved?
+    !moved_to.nil?
+  end
+
+  def can_move?(user, to_project = nil)
+    if to_project
+      return false unless user.can?(:admin_issue, to_project)
+    end
+
+    !moved? && user.can?(:admin_issue, self.project)
+  end
+
   def to_branch_name
     "#{title.parameterize}-#{iid}"
   end
diff --git a/app/models/user.rb b/app/models/user.rb
index c011af03591..9c315cfe966 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -435,7 +435,7 @@ class User < ActiveRecord::Base
     Group.where("namespaces.id IN (#{union.to_sql})")
   end
 
-  # Returns the groups a user is authorized to access.
+  # Returns projects user is authorized to access.
   def authorized_projects
     Project.where("projects.id IN (#{projects_union.to_sql})")
   end
diff --git a/app/services/git_push_service.rb b/app/services/git_push_service.rb
index 14e2a2c0699..c007d648dd6 100644
--- a/app/services/git_push_service.rb
+++ b/app/services/git_push_service.rb
@@ -120,7 +120,7 @@ class GitPushService < BaseService
         closed_issues = commit.closes_issues(current_user)
         closed_issues.each do |issue|
           if can?(current_user, :update_issue, issue)
-            Issues::CloseService.new(project, authors[commit], {}).execute(issue, commit)
+            Issues::CloseService.new(project, authors[commit], {}).execute(issue, commit: commit)
           end
         end
       end
diff --git a/app/services/issues/close_service.rb b/app/services/issues/close_service.rb
index 78254b49af3..859c934ea3b 100644
--- a/app/services/issues/close_service.rb
+++ b/app/services/issues/close_service.rb
@@ -1,6 +1,6 @@
 module Issues
   class CloseService < Issues::BaseService
-    def execute(issue, commit = nil)
+    def execute(issue, commit: nil, notifications: true, system_note: true)
       if project.jira_tracker? && project.jira_service.active
         project.jira_service.execute(commit, issue)
         todo_service.close_issue(issue, current_user)
@@ -9,8 +9,8 @@ module Issues
 
       if project.default_issues_tracker? && issue.close
         event_service.close_issue(issue, current_user)
-        create_note(issue, commit)
-        notification_service.close_issue(issue, current_user)
+        create_note(issue, commit) if system_note
+        notification_service.close_issue(issue, current_user) if notifications
         todo_service.close_issue(issue, current_user)
         execute_hooks(issue, 'close')
       end
diff --git a/app/services/issues/create_service.rb b/app/services/issues/create_service.rb
index 10787e8873c..e63e1af8766 100644
--- a/app/services/issues/create_service.rb
+++ b/app/services/issues/create_service.rb
@@ -4,7 +4,7 @@ module Issues
       filter_params
       label_params = params[:label_ids]
       issue = project.issues.new(params.except(:label_ids))
-      issue.author = current_user
+      issue.author = params[:author] || current_user
 
       if issue.save
         issue.update_attributes(label_ids: label_params)
diff --git a/app/services/issues/move_service.rb b/app/services/issues/move_service.rb
new file mode 100644
index 00000000000..3cfbafe1576
--- /dev/null
+++ b/app/services/issues/move_service.rb
@@ -0,0 +1,94 @@
+module Issues
+  class MoveService < Issues::BaseService
+    class MoveError < StandardError; end
+
+    def execute(issue, new_project)
+      @old_issue = issue
+      @old_project = @project
+      @new_project = new_project
+
+      unless issue.can_move?(current_user, new_project)
+        raise MoveError, 'Cannot move issue due to insufficient permissions!'
+      end
+
+      if @project == new_project
+        raise MoveError, 'Cannot move issue to project it originates from!'
+      end
+
+      # Using transaction because of a high resources footprint
+      # on rewriting notes (unfolding references)
+      #
+      ActiveRecord::Base.transaction do
+        # New issue tasks
+        #
+        @new_issue = create_new_issue
+
+        rewrite_notes
+        add_note_moved_from
+
+        # Old issue tasks
+        #
+        add_note_moved_to
+        close_issue
+        mark_as_moved
+      end
+
+      notify_participants
+
+      @new_issue
+    end
+
+    private
+
+    def create_new_issue
+      new_params = { id: nil, iid: nil, label_ids: [], milestone: nil,
+                     project: @new_project, author: @old_issue.author,
+                     description: unfold_references(@old_issue.description) }
+
+      new_params = @old_issue.serializable_hash.merge(new_params)
+      CreateService.new(@new_project, @current_user, new_params).execute
+    end
+
+    def rewrite_notes
+      @old_issue.notes.find_each do |note|
+        new_note = note.dup
+        new_params = { project: @new_project, noteable: @new_issue,
+                       note: unfold_references(new_note.note),
+                       created_at: note.created_at }
+
+        new_note.update(new_params)
+      end
+    end
+
+    def close_issue
+      close_service = CloseService.new(@old_project, @current_user)
+      close_service.execute(@old_issue, notifications: false, system_note: false)
+    end
+
+    def add_note_moved_from
+      SystemNoteService.noteable_moved(@new_issue, @new_project,
+                                       @old_issue, @current_user,
+                                       direction: :from)
+    end
+
+    def add_note_moved_to
+      SystemNoteService.noteable_moved(@old_issue, @old_project,
+                                       @new_issue, @current_user,
+                                       direction: :to)
+    end
+
+    def unfold_references(content)
+      rewriter = Gitlab::Gfm::ReferenceRewriter.new(content, @old_project,
+                                                    @current_user)
+      rewriter.rewrite(@new_project)
+    end
+
+    def notify_participants
+      notification_service.issue_moved(@old_issue, @new_issue, @current_user)
+    end
+
+    def mark_as_moved
+      @old_issue.update(moved_to: @new_issue)
+    end
+  end
+end
diff --git a/app/services/merge_requests/post_merge_service.rb b/app/services/merge_requests/post_merge_service.rb
index ebb67c7db65..064910f81f7 100644
--- a/app/services/merge_requests/post_merge_service.rb
+++ b/app/services/merge_requests/post_merge_service.rb
@@ -22,7 +22,7 @@ module MergeRequests
       closed_issues = merge_request.closes_issues(current_user)
       closed_issues.each do |issue|
         if can?(current_user, :update_issue, issue)
-          Issues::CloseService.new(project, current_user, {}).execute(issue, merge_request)
+          Issues::CloseService.new(project, current_user, {}).execute(issue, commit: merge_request)
         end
       end
     end
diff --git a/app/services/notification_service.rb b/app/services/notification_service.rb
index 19a6779dea9..3bdf00a8291 100644
--- a/app/services/notification_service.rb
+++ b/app/services/notification_service.rb
@@ -236,6 +236,16 @@ class NotificationService
     end
   end
 
+  def issue_moved(issue, new_issue, current_user)
+    recipients = build_recipients(issue, issue.project, current_user)
+
+    recipients.map do |recipient|
+      email = mailer.issue_moved_email(recipient, issue, new_issue, current_user)
+      email.deliver_later
+      email
+    end
+  end
+
   protected
 
   # Get project users with WATCH notification level
diff --git a/app/services/system_note_service.rb b/app/services/system_note_service.rb
index c644cd0b951..e022a046c48 100644
--- a/app/services/system_note_service.rb
+++ b/app/services/system_note_service.rb
@@ -411,4 +411,26 @@ class SystemNoteService
     body = "Marked the task **#{new_task.source}** as #{status_label}"
     create_note(noteable: noteable, project: project, author: author, note: body)
   end
+
+  # Called when noteable has been moved to another project
+  #
+  # direction    - symbol, :to or :from
+  # noteable     - Noteable object
+  # noteable_ref - Referenced noteable
+  # author       - User performing the move
+  #
+  # Example Note text:
+  #
+  #   "Moved to some_namespace/project_new#11"
+  #
+  # Returns the created Note object
+  def self.noteable_moved(noteable, project, noteable_ref, author, direction:)
+    unless [:to, :from].include?(direction)
+      raise ArgumentError, "Invalid direction `#{direction}`"
+    end
+
+    cross_reference = noteable_ref.to_reference(project)
+    body = "Moved #{direction} #{cross_reference}"
+    create_note(noteable: noteable, project: project, author: author, note: body)
+  end
 end
diff --git a/app/views/notify/issue_moved_email.html.haml b/app/views/notify/issue_moved_email.html.haml
new file mode 100644
index 00000000000..40f7d61fe19
--- /dev/null
+++ b/app/views/notify/issue_moved_email.html.haml
@@ -0,0 +1,6 @@
+%p
+  Issue was moved to another project.
+%p
+  New issue:
+  = link_to namespace_project_issue_url(@new_project.namespace, @new_project, @new_issue) do
+    = @new_issue.title
diff --git a/app/views/notify/issue_moved_email.text.erb b/app/views/notify/issue_moved_email.text.erb
new file mode 100644
index 00000000000..b3bd43c2055
--- /dev/null
+++ b/app/views/notify/issue_moved_email.text.erb
@@ -0,0 +1,4 @@
+Issue was moved to another project.
+
+New issue location:
+<%= namespace_project_issue_url(@new_project.namespace, @new_project, @new_issue) %>
diff --git a/app/views/shared/issuable/_form.html.haml b/app/views/shared/issuable/_form.html.haml
index 80418e69d9c..1740b128ee4 100644
--- a/app/views/shared/issuable/_form.html.haml
+++ b/app/views/shared/issuable/_form.html.haml
@@ -85,13 +85,26 @@
       - if can? current_user, :admin_label, issuable.project
         = link_to 'Create new label', new_namespace_project_label_path(issuable.project.namespace, issuable.project), target: :blank
 
+- if issuable.can_move?(current_user)
+  %hr
+  .form-group
+    = label_tag :move_to_project_id, 'Move', class: 'control-label'
+    .col-sm-10
+      - projects = project_options(issuable, current_user, ability: :admin_issue)
+      = select_tag(:move_to_project_id, projects, include_blank: true,
+                   class: 'select2', data: { placeholder: 'Select project' })
+      &nbsp;
+      %span{ data: { toggle: 'tooltip', placement: 'auto top' }, style: 'cursor: default',
+      title: 'Moving an issue will copy the discussion to a different project and close it here. All participants will be notified of the new location.' }
+        = icon('question-circle')
+
 - if issuable.is_a?(MergeRequest)
   %hr
-    - if @merge_request.new_record?
-      .form-group
-        = f.label :source_branch, class: 'control-label'
-        .col-sm-10
-          = f.select(:source_branch, [@merge_request.source_branch], { }, { class: 'source_branch select2 span2', disabled: true })
+  - if @merge_request.new_record?
+    .form-group
+      = f.label :source_branch, class: 'control-label'
+      .col-sm-10
+        = f.select(:source_branch, [@merge_request.source_branch], { }, { class: 'source_branch select2 span2', disabled: true })
   .form-group
     = f.label :target_branch, class: 'control-label'
     .col-sm-10
diff --git a/db/migrate/20160317092222_add_moved_to_to_issue.rb b/db/migrate/20160317092222_add_moved_to_to_issue.rb
new file mode 100644
index 00000000000..461e7fb3a9b
--- /dev/null
+++ b/db/migrate/20160317092222_add_moved_to_to_issue.rb
@@ -0,0 +1,5 @@
+class AddMovedToToIssue < ActiveRecord::Migration
+  def change
+    add_reference :issues, :moved_to, references: :issues
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 5b2f5aa3ddd..36b37d3944c 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160316204731) do
+ActiveRecord::Schema.define(version: 20160317092222) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -416,6 +416,7 @@ ActiveRecord::Schema.define(version: 20160316204731) do
     t.string   "state"
     t.integer  "iid"
     t.integer  "updated_by_id"
+    t.integer  "moved_to_id"
     t.boolean  "confidential",              default: false
   end
 
diff --git a/lib/banzai/filter/reference_filter.rb b/lib/banzai/filter/reference_filter.rb
index 3637b1bac94..132f0a4bd93 100644
--- a/lib/banzai/filter/reference_filter.rb
+++ b/lib/banzai/filter/reference_filter.rb
@@ -47,6 +47,7 @@ module Banzai
       # Returns a String
       def data_attribute(attributes = {})
         attributes[:reference_filter] = self.class.name.demodulize
+        attributes.delete(:original) if context[:no_original_data]
         attributes.map { |key, value| %Q(data-#{key.to_s.dasherize}="#{escape_once(value)}") }.join(" ")
       end
 
diff --git a/lib/gitlab/gfm/reference_rewriter.rb b/lib/gitlab/gfm/reference_rewriter.rb
new file mode 100644
index 00000000000..a1c6ee7bd69
--- /dev/null
+++ b/lib/gitlab/gfm/reference_rewriter.rb
@@ -0,0 +1,79 @@
+module Gitlab
+  module Gfm
+    ##
+    # Class that unfolds local references in text.
+    #
+    # The initializer takes text in Markdown and project this text is valid
+    # in context of.
+    #
+    # `unfold` method tries to find all local references and unfold each of
+    # those local references to cross reference format, assuming that the
+    # argument passed to this method is a project that references will be
+    # viewed from (see `Referable#to_reference method).
+    #
+    # Examples:
+    #
+    # 'Hello, this issue is related to #123 and
+    #  other issues labeled with ~"label"', will be converted to:
+    #
+    # 'Hello, this issue is related to gitlab-org/gitlab-ce#123 and
+    #  other issue labeled with gitlab-org/gitlab-ce~"label"'.
+    #
+    # It does respect markdown lexical rules, so text in code block will not be
+    # replaced, see another example:
+    #
+    # 'Merge request for issue #1234, see also link:
+    #  http://gitlab.com/some/link/#1234, and code `puts #1234`' =>
+    #
+    # 'Merge request for issue gitlab-org/gitlab-ce#1234, se also link:
+    #  http://gitlab.com/some/link/#1234, and code `puts #1234`'
+    #
+    class ReferenceRewriter
+      def initialize(text, source_project, current_user)
+        @text = text
+        @source_project = source_project
+        @current_user = current_user
+        @original_html = markdown(text)
+      end
+
+      def rewrite(target_project)
+        pattern = Gitlab::ReferenceExtractor.references_pattern
+
+        @text.gsub(pattern) do |reference|
+          unfold_reference(reference, Regexp.last_match, target_project)
+        end
+      end
+
+      private
+
+      def unfold_reference(reference, match, target_project)
+        before = @text[0...match.begin(0)]
+        after = @text[match.end(0)..-1]
+
+        referable = find_referable(reference)
+        return reference unless referable
+
+        cross_reference = referable.to_reference(target_project)
+        return reference if reference == cross_reference
+
+        new_text = before + cross_reference + after
+        substitution_valid?(new_text) ? cross_reference : reference
+      end
+
+      def find_referable(reference)
+        extractor = Gitlab::ReferenceExtractor.new(@source_project,
+                                                   @current_user)
+        extractor.analyze(reference)
+        extractor.all.first
+      end
+
+      def substitution_valid?(substituted)
+        @original_html == markdown(substituted)
+      end
+
+      def markdown(text)
+        Banzai.render(text, project: @source_project, no_original_data: true)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/reference_extractor.rb b/lib/gitlab/reference_extractor.rb
index 4d830aa45e1..13c4d64c99b 100644
--- a/lib/gitlab/reference_extractor.rb
+++ b/lib/gitlab/reference_extractor.rb
@@ -1,6 +1,7 @@
 module Gitlab
   # Extract possible GFM references from an arbitrary String for further processing.
   class ReferenceExtractor < Banzai::ReferenceExtractor
+    REFERABLES = %i(user issue label milestone merge_request snippet commit commit_range)
     attr_accessor :project, :current_user, :author
 
     def initialize(project, current_user = nil, author = nil)
@@ -17,7 +18,7 @@ module Gitlab
       super(text, context.merge(project: project))
     end
 
-    %i(user label milestone merge_request snippet commit commit_range).each do |type|
+    REFERABLES.each do |type|
       define_method("#{type}s") do
         @references[type] ||= references(type, reference_context)
       end
@@ -31,6 +32,21 @@ module Gitlab
       end
     end
 
+    def all
+      REFERABLES.each { |referable| send(referable.to_s.pluralize) }
+      @references.values.flatten
+    end
+
+    def self.references_pattern
+      return @pattern if @pattern
+
+      patterns = REFERABLES.map do |ref|
+        ref.to_s.classify.constantize.try(:reference_pattern)
+      end
+
+      @pattern = Regexp.union(patterns.compact)
+    end
+
     private
 
     def reference_context
diff --git a/spec/features/issues/move_spec.rb b/spec/features/issues/move_spec.rb
new file mode 100644
index 00000000000..6fda0c31866
--- /dev/null
+++ b/spec/features/issues/move_spec.rb
@@ -0,0 +1,87 @@
+require 'rails_helper'
+
+feature 'issue move to another project' do
+  let(:user) { create(:user) }
+  let(:old_project) { create(:project) }
+  let(:text) { 'Some issue description' }
+
+  let(:issue) do
+    create(:issue, description: text, project: old_project, author: user)
+  end
+
+  background { login_as(user) }
+
+  context 'user does not have permission to move issue' do
+    background do
+      old_project.team << [user, :guest]
+
+      edit_issue(issue)
+    end
+
+    scenario 'moving issue to another project not allowed' do
+      expect(page).to have_no_select('move_to_project_id')
+    end
+  end
+
+  context 'user has permission to move issue' do
+    let!(:mr) { create(:merge_request, source_project: old_project) }
+    let(:new_project) { create(:project) }
+    let(:text) { 'Text with !1' }
+    let(:cross_reference) { old_project.to_reference }
+
+    background do
+      old_project.team << [user, :reporter]
+      new_project.team << [user, :reporter]
+
+      edit_issue(issue)
+    end
+
+    scenario 'moving issue to another project' do
+      select(new_project.name_with_namespace, from: 'move_to_project_id')
+      click_button('Save changes')
+
+      expect(current_url).to include project_path(new_project)
+
+      page.within('.issue') do
+        expect(page).to have_content("Text with #{cross_reference}!1")
+        expect(page).to have_content("Moved from #{cross_reference}#1")
+        expect(page).to have_content(issue.title)
+      end
+    end
+
+    context 'projects user does not have permission to move issue to exist' do
+      let!(:private_project) { create(:project, :private) }
+      let(:another_project) { create(:project) }
+      background { another_project.team << [user, :guest] }
+
+      scenario 'browsing projects in projects select' do
+        options = [ '', 'No project', new_project.name_with_namespace ]
+        expect(page).to have_select('move_to_project_id', options: options)
+      end
+    end
+
+    context 'issue has been already moved' do
+      let(:new_issue) { create(:issue, project: new_project) }
+      let(:issue) do
+        create(:issue, project: old_project, author: user, moved_to: new_issue)
+      end
+
+      scenario 'user wants to move issue that has already been moved' do
+        expect(page).to have_no_select('move_to_project_id')
+      end
+    end
+  end
+
+  def edit_issue(issue)
+    visit issue_path(issue)
+    page.within('.issuable-header') { click_link 'Edit' }
+  end
+
+  def issue_path(issue)
+    namespace_project_issue_path(issue.project.namespace, issue.project, issue)
+  end
+
+  def project_path(project)
+    namespace_project_path(new_project.namespace, new_project)
+  end
+end
diff --git a/spec/lib/gitlab/gfm/reference_rewriter_spec.rb b/spec/lib/gitlab/gfm/reference_rewriter_spec.rb
new file mode 100644
index 00000000000..0a7ca3ec848
--- /dev/null
+++ b/spec/lib/gitlab/gfm/reference_rewriter_spec.rb
@@ -0,0 +1,89 @@
+require 'spec_helper'
+
+describe Gitlab::Gfm::ReferenceRewriter do
+  let(:text) { 'some text' }
+  let(:old_project) { create(:project) }
+  let(:new_project) { create(:project) }
+  let(:user) { create(:user) }
+
+  before { old_project.team << [user, :guest] }
+
+  describe '#rewrite' do
+    subject do
+      described_class.new(text, old_project, user).rewrite(new_project)
+    end
+
+    context 'multiple issues and merge requests referenced' do
+      let!(:issue_first) { create(:issue, project: old_project) }
+      let!(:issue_second) { create(:issue, project: old_project) }
+      let!(:merge_request) { create(:merge_request, source_project: old_project) }
+
+      context 'plain text description' do
+        let(:text) { 'Description that references #1, #2 and !1' }
+
+        it { is_expected.to include issue_first.to_reference(new_project) }
+        it { is_expected.to include issue_second.to_reference(new_project) }
+        it { is_expected.to include merge_request.to_reference(new_project) }
+      end
+
+      context 'description with ignored elements' do
+        let(:text) do
+          "Hi. This references #1, but not `#2`\n" +
+          '<pre>and not !1</pre>'
+        end
+
+        it { is_expected.to include issue_first.to_reference(new_project) }
+        it { is_expected.to_not include issue_second.to_reference(new_project) }
+        it { is_expected.to_not include merge_request.to_reference(new_project) }
+      end
+
+      context 'description ambigous elements' do
+        context 'url' do
+          let(:url) { 'http://gitlab.com/#1' }
+          let(:text) { "This references #1, but not #{url}" }
+
+          it { is_expected.to include url }
+        end
+
+        context 'code' do
+          let(:text) { "#1, but not `[#1]`" }
+          it { is_expected.to eq "#{issue_first.to_reference(new_project)}, but not `[#1]`" }
+        end
+
+        context 'code reverse' do
+          let(:text) { "not `#1`, but #1" }
+          it { is_expected.to eq "not `#1`, but #{issue_first.to_reference(new_project)}" }
+        end
+
+        context 'code in random order' do
+          let(:text) { "#1, `#1`, #1, `#1`" }
+          let(:ref) { issue_first.to_reference(new_project) }
+
+          it { is_expected.to eq "#{ref}, `#1`, #{ref}, `#1`" }
+        end
+
+        context 'description with labels' do
+          let!(:label) { create(:label, id: 123, name: 'test', project: old_project) }
+          let(:project_ref) { old_project.to_reference }
+
+          context 'label referenced by id' do
+            let(:text) { '#1 and ~123' }
+            it { is_expected.to eq %Q{#{project_ref}#1 and #{project_ref}~123} }
+          end
+
+          context 'label referenced by text' do
+            let(:text) { '#1 and ~"test"' }
+            it { is_expected.to eq %Q{#{project_ref}#1 and #{project_ref}~123} }
+          end
+        end
+      end
+
+      context 'reference contains milestone' do
+        let(:milestone) { create(:milestone) }
+        let(:text) { "milestone ref: #{milestone.to_reference}" }
+
+        it { is_expected.to eq text }
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/reference_extractor_spec.rb b/spec/lib/gitlab/reference_extractor_spec.rb
index 65af37e24f1..7c617723e6d 100644
--- a/spec/lib/gitlab/reference_extractor_spec.rb
+++ b/spec/lib/gitlab/reference_extractor_spec.rb
@@ -124,4 +124,24 @@ describe Gitlab::ReferenceExtractor, lib: true do
       expect(extracted).to match_array([issue])
     end
   end
+
+  describe '#all' do
+    let(:issue) { create(:issue, project: project) }
+    let(:label) { create(:label, project: project) }
+    let(:text) { "Ref. #{issue.to_reference} and #{label.to_reference}" }
+
+    before do
+      project.team << [project.creator, :developer]
+      subject.analyze(text)
+    end
+
+    it 'returns all referables' do
+      expect(subject.all).to match_array([issue, label])
+    end
+  end
+
+  describe '.references_pattern' do
+    subject { described_class.references_pattern }
+    it { is_expected.to be_kind_of Regexp }
+  end
 end
diff --git a/spec/mailers/notify_spec.rb b/spec/mailers/notify_spec.rb
index f910424d85b..9b47acfe0cd 100644
--- a/spec/mailers/notify_spec.rb
+++ b/spec/mailers/notify_spec.rb
@@ -158,6 +158,33 @@ describe Notify do
             is_expected.to have_body_text /#{namespace_project_issue_path project.namespace, project, issue}/
           end
         end
+
+        describe 'moved to another project' do
+          let(:new_issue) { create(:issue) }
+          subject { Notify.issue_moved_email(recipient, issue, new_issue, current_user) }
+
+          it_behaves_like 'an answer to an existing thread', 'issue'
+          it_behaves_like 'it should show Gmail Actions View Issue link'
+          it_behaves_like 'an unsubscribeable thread'
+
+          it 'contains description about action taken' do
+            is_expected.to have_body_text 'Issue was moved to another project'
+          end
+
+          it 'has the correct subject' do
+            is_expected.to have_subject /#{issue.title} \(##{issue.iid}\)/i
+          end
+
+          it 'contains link to new issue' do
+            new_issue_url = namespace_project_issue_path(new_issue.project.namespace,
+                                                         new_issue.project, new_issue)
+            is_expected.to have_body_text new_issue_url
+          end
+
+          it 'contains a link to the original issue' do
+            is_expected.to have_body_text /#{namespace_project_issue_path project.namespace, project, issue}/
+          end
+        end
       end
 
       context 'for merge requests' do
diff --git a/spec/models/issue_spec.rb b/spec/models/issue_spec.rb
index 540a62eb1f8..05e4233243d 100644
--- a/spec/models/issue_spec.rb
+++ b/spec/models/issue_spec.rb
@@ -130,6 +130,56 @@ describe Issue, models: true do
     end
   end
 
+  describe '#can_move?' do
+    let(:user) { create(:user) }
+    let(:issue) { create(:issue) }
+    subject { issue.can_move?(user) }
+
+    context 'user is not a member of project issue belongs to' do
+      it { is_expected.to eq false}
+    end
+
+    context 'user is reporter in project issue belongs to' do
+      let(:project) { create(:project) }
+      let(:issue) { create(:issue, project: project) }
+
+      before { project.team << [user, :reporter] }
+
+      it { is_expected.to eq true }
+
+      context 'checking destination project also' do
+        subject { issue.can_move?(user, to_project) }
+        let(:to_project) { create(:project) }
+
+        context 'destination project allowed' do
+          before { to_project.team << [user, :reporter] }
+          it { is_expected.to eq true }
+        end
+
+        context 'destination project not allowed' do
+          before { to_project.team << [user, :guest] }
+          it { is_expected.to eq false }
+        end
+      end
+    end
+  end
+
+  describe '#moved?' do
+    let(:issue) { create(:issue) }
+    subject { issue.moved? }
+
+    context 'issue not moved' do
+      it { is_expected.to eq false }
+    end
+
+    context 'issue already moved' do
+      let(:moved_to_issue) { create(:issue) }
+      let(:issue) { create(:issue, moved_to: moved_to_issue) }
+
+      it { is_expected.to eq true }
+    end
+  end
+
   describe '#related_branches' do
     it "selects the right branches" do
       allow(subject.project.repository).to receive(:branch_names).
diff --git a/spec/services/issues/move_service_spec.rb b/spec/services/issues/move_service_spec.rb
new file mode 100644
index 00000000000..14cc20e529a
--- /dev/null
+++ b/spec/services/issues/move_service_spec.rb
@@ -0,0 +1,213 @@
+require 'spec_helper'
+
+describe Issues::MoveService, services: true do
+  let(:user) { create(:user) }
+  let(:author) { create(:user) }
+  let(:title) { 'Some issue' }
+  let(:description) { 'Some issue description' }
+  let(:old_project) { create(:project) }
+  let(:new_project) { create(:project) }
+
+  let(:old_issue) do
+    create(:issue, title: title, description: description,
+                   project: old_project, author: author)
+  end
+
+  let(:move_service) do
+    described_class.new(old_project, user)
+  end
+
+  shared_context 'user can move issue' do
+    before do
+      old_project.team << [user, :reporter]
+      new_project.team << [user, :reporter]
+    end
+  end
+
+  describe '#execute' do
+    shared_context 'issue move executed' do
+      let!(:new_issue) { move_service.execute(old_issue, new_project) }
+    end
+
+    context 'issue movable' do
+      include_context 'user can move issue'
+
+      context 'generic issue' do
+        include_context 'issue move executed'
+
+        it 'creates a new issue in a new project' do
+          expect(new_issue.project).to eq new_project
+        end
+
+        it 'rewrites issue title' do
+          expect(new_issue.title).to eq title
+        end
+
+        it 'rewrites issue description' do
+          expect(new_issue.description).to eq description
+        end
+
+        it 'adds system note to old issue at the end' do
+          expect(old_issue.notes.last.note).to match /^Moved to/
+        end
+
+        it 'adds system note to new issue at the end' do
+          expect(new_issue.notes.last.note).to match /^Moved from/
+        end
+
+        it 'closes old issue' do
+          expect(old_issue.closed?).to be true
+        end
+
+        it 'persists new issue' do
+          expect(new_issue.persisted?).to be true
+        end
+
+        it 'persists all changes' do
+          expect(old_issue.changed?).to be false
+          expect(new_issue.changed?).to be false
+        end
+
+        it 'preserves author' do
+          expect(new_issue.author).to eq author
+        end
+
+        it 'removes data that is invalid in new context' do
+          expect(new_issue.milestone).to be_nil
+          expect(new_issue.labels).to be_empty
+        end
+
+        it 'creates a new internal id for issue' do
+          expect(new_issue.iid).to be 1
+        end
+
+        it 'marks issue as moved' do
+          expect(old_issue.moved?).to eq true
+          expect(old_issue.moved_to).to eq new_issue
+        end
+      end
+
+      context 'issue with notes' do
+        context 'notes without references' do
+          let(:notes_params) do
+            [{ system: false, note: 'Some comment 1' },
+             { system: true, note: 'Some system note' },
+             { system: false, note: 'Some comment 2' }]
+          end
+
+          let(:notes_contents) { notes_params.map { |n| n[:note] } }
+
+          before do
+            note_params = { noteable: old_issue, project: old_project, author: author }
+            notes_params.each do |note|
+              create(:note, note_params.merge(note))
+            end
+          end
+
+          include_context 'issue move executed'
+
+          let(:all_notes) { new_issue.notes.order('id ASC') }
+          let(:system_notes) { all_notes.system }
+          let(:user_notes) { all_notes.user }
+
+          it 'rewrites existing notes in valid order' do
+            expect(all_notes.pluck(:note).first(3)).to eq notes_contents
+          end
+
+          it 'adds a system note about move after rewritten notes' do
+            expect(system_notes.last.note).to match /^Moved from/
+          end
+
+          it 'preserves orignal author of comment' do
+            expect(user_notes.pluck(:author_id)).to all(eq(author.id))
+          end
+
+          it 'preserves time when note has been created at' do
+            expect(old_issue.notes.first.created_at)
+              .to eq new_issue.notes.first.created_at
+          end
+        end
+
+        context 'notes with references' do
+          before do
+            create(:merge_request, source_project: old_project)
+            create(:note, noteable: old_issue, project: old_project, author: author,
+                          note: 'Note with reference to merge request !1')
+          end
+
+          include_context 'issue move executed'
+          let(:new_note) { new_issue.notes.first }
+
+          it 'rewrites references using a cross reference to old project' do
+            expect(new_note.note)
+              .to eq "Note with reference to merge request #{old_project.to_reference}!1"
+          end
+        end
+      end
+
+      describe 'rewritting references' do
+        include_context 'issue move executed'
+
+        context 'issue reference' do
+          let(:another_issue) { create(:issue, project: old_project) }
+          let(:description) { "Some description #{another_issue.to_reference}" }
+
+          it 'rewrites referenced issues creating cross project reference' do
+            expect(new_issue.description)
+              .to eq "Some description #{old_project.to_reference}#{another_issue.to_reference}"
+          end
+        end
+      end
+
+      context 'moving to same project' do
+        let(:new_project) { old_project }
+
+        it 'raises error' do
+          expect { move_service.execute(old_issue, new_project) }
+            .to raise_error(StandardError, /Cannot move issue/)
+        end
+      end
+    end
+
+    describe 'move permissions' do
+      let(:move) { move_service.execute(old_issue, new_project) }
+
+      context 'user is reporter in both projects' do
+        include_context 'user can move issue'
+        it { expect { move }.to_not raise_error }
+      end
+
+      context 'user is reporter only in new project' do
+        before { new_project.team << [user, :reporter] }
+        it { expect { move }.to raise_error(StandardError, /permissions/) }
+      end
+
+      context 'user is reporter only in old project' do
+        before { old_project.team << [user, :reporter] }
+        it { expect { move }.to raise_error(StandardError, /permissions/) }
+      end
+
+      context 'user is reporter in one project and guest in another' do
+        before do
+          new_project.team << [user, :guest]
+          old_project.team << [user, :reporter]
+        end
+
+        it { expect { move }.to raise_error(StandardError, /permissions/) }
+      end
+
+      context 'issue has already been moved' do
+        include_context 'user can move issue'
+
+        let(:moved_to_issue) { create(:issue) }
+
+        let(:old_issue) do
+          create(:issue, project: old_project, author: author,
+                         moved_to: moved_to_issue)
+        end
+
+        it { expect { move }.to raise_error(StandardError, /permissions/) }
+      end
+    end
+  end
+end
diff --git a/spec/services/system_note_service_spec.rb b/spec/services/system_note_service_spec.rb
index 8e6292014d4..240eae10052 100644
--- a/spec/services/system_note_service_spec.rb
+++ b/spec/services/system_note_service_spec.rb
@@ -453,6 +453,59 @@ describe SystemNoteService, services: true do
     end
   end
 
+  describe '.noteable_moved' do
+    let(:new_project) { create(:project) }
+    let(:new_noteable) { create(:issue, project: new_project) }
+
+    subject do
+      described_class.noteable_moved(noteable, project, new_noteable, author, direction: direction)
+    end
+
+    shared_examples 'cross project mentionable' do
+      include GitlabMarkdownHelper
+
+      it 'should contain cross reference to new noteable' do
+        expect(subject.note).to include cross_project_reference(new_project, new_noteable)
+      end
+
+      it 'should mention referenced noteable' do
+        expect(subject.note).to include new_noteable.to_reference
+      end
+
+      it 'should mention referenced project' do
+        expect(subject.note).to include new_project.to_reference
+      end
+    end
+
+    context 'moved to' do
+      let(:direction) { :to }
+
+      it_behaves_like 'cross project mentionable'
+
+      it 'should notify about noteable being moved to' do
+        expect(subject.note).to match /Moved to/
+      end
+    end
+
+    context 'moved from' do
+      let(:direction) { :from }
+
+      it_behaves_like 'cross project mentionable'
+
+      it 'should notify about noteable being moved from' do
+        expect(subject.note).to match /Moved from/
+      end
+    end
+
+    context 'invalid direction' do
+      let(:direction) { :invalid }
+
+      it 'should raise error' do
+        expect { subject }.to raise_error StandardError, /Invalid direction/
+      end
+    end
+  end
+
   include JiraServiceHelper
 
   describe 'JIRA integration' do