Merge branch '45663-tag-quick-action-on-commit-comments' into 'master'

Resolve "`/tag` quick action on Commit comments"

Closes #45663

See merge request gitlab-org/gitlab-ce!20694

23 files changed, 524 insertions, 102 deletions

diff --git a/app/controllers/projects/autocomplete_sources_controller.rb b/app/controllers/projects/autocomplete_sources_controller.rb
index 07627ffb69f..a8f73ed5cb0 100644
--- a/app/controllers/projects/autocomplete_sources_controller.rb
+++ b/app/controllers/projects/autocomplete_sources_controller.rb
@@ -32,13 +32,8 @@ class Projects::AutocompleteSourcesController < Projects::ApplicationController
   end
 
   def target
-    case params[:type]&.downcase
-    when 'issue'
-      IssuesFinder.new(current_user, project_id: @project.id).find_by(iid: params[:type_id])
-    when 'mergerequest'
-      MergeRequestsFinder.new(current_user, project_id: @project.id).find_by(iid: params[:type_id])
-    when 'commit'
-      @project.commit(params[:type_id])
-    end
+    QuickActions::TargetService
+      .new(project, current_user)
+      .execute(params[:type], params[:type_id])
   end
 end
diff --git a/app/models/commit.rb b/app/models/commit.rb
index 8b9f4490ffa..27fbdc3e386 100644
--- a/app/models/commit.rb
+++ b/app/models/commit.rb
@@ -448,6 +448,10 @@ class Commit
     true
   end
 
+  def to_ability_name
+    model_name.singular
+  end
+
   def touch
     # no-op but needs to be defined since #persisted? is defined
   end
diff --git a/app/models/system_note_metadata.rb b/app/models/system_note_metadata.rb
index c5c77bc8333..376ef673ca8 100644
--- a/app/models/system_note_metadata.rb
+++ b/app/models/system_note_metadata.rb
@@ -15,7 +15,7 @@ class SystemNoteMetadata < ActiveRecord::Base
     commit description merge confidential visible label assignee cross_reference
     title time_tracking branch milestone discussion task moved
     opened closed merged duplicate locked unlocked
-    outdated
+    outdated tag
   ].freeze
 
   validates :note, presence: true
diff --git a/app/policies/commit_policy.rb b/app/policies/commit_policy.rb
new file mode 100644
index 00000000000..67e9bc12804
--- /dev/null
+++ b/app/policies/commit_policy.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class CommitPolicy < BasePolicy
+  delegate { @subject.project }
+end
diff --git a/app/services/commits/tag_service.rb b/app/services/commits/tag_service.rb
new file mode 100644
index 00000000000..7961ba4d3c4
--- /dev/null
+++ b/app/services/commits/tag_service.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module Commits
+  class TagService < BaseService
+    def execute(commit)
+      unless params[:tag_name]
+        return error('Missing parameter tag_name')
+      end
+
+      tag_name = params[:tag_name]
+      message = params[:tag_message]
+      release_description = nil
+
+      result = Tags::CreateService
+        .new(commit.project, current_user)
+        .execute(tag_name, commit.sha, message, release_description)
+
+      if result[:status] == :success
+        tag = result[:tag]
+        SystemNoteService.tag_commit(commit, commit.project, current_user, tag.name)
+      end
+
+      result
+    end
+  end
+end
diff --git a/app/services/notes/quick_actions_service.rb b/app/services/notes/quick_actions_service.rb
index 7280449bb1c..4c14d834949 100644
--- a/app/services/notes/quick_actions_service.rb
+++ b/app/services/notes/quick_actions_service.rb
@@ -4,7 +4,8 @@ module Notes
   class QuickActionsService < BaseService
     UPDATE_SERVICES = {
       'Issue' => Issues::UpdateService,
-      'MergeRequest' => MergeRequests::UpdateService
+      'MergeRequest' => MergeRequests::UpdateService,
+      'Commit' => Commits::TagService
     }.freeze
 
     def self.noteable_update_service(note)
diff --git a/app/services/preview_markdown_service.rb b/app/services/preview_markdown_service.rb
index a15ee4911ef..11b996ed4b6 100644
--- a/app/services/preview_markdown_service.rb
+++ b/app/services/preview_markdown_service.rb
@@ -16,7 +16,7 @@ class PreviewMarkdownService < BaseService
   private
 
   def explain_quick_actions(text)
-    return text, [] unless %w(Issue MergeRequest).include?(commands_target_type)
+    return text, [] unless %w(Issue MergeRequest Commit).include?(commands_target_type)
 
     quick_actions_service = QuickActions::InterpretService.new(project, current_user)
     quick_actions_service.explain(text, find_commands_target)
@@ -29,13 +29,9 @@ class PreviewMarkdownService < BaseService
   end
 
   def find_commands_target
-    if commands_target_id.present?
-      finder = commands_target_type == 'Issue' ? IssuesFinder : MergeRequestsFinder
-      finder.new(current_user, project_id: project.id).find(commands_target_id)
-    else
-      collection = commands_target_type == 'Issue' ? project.issues : project.merge_requests
-      collection.build
-    end
+    QuickActions::TargetService
+      .new(project, current_user)
+      .execute(commands_target_type, commands_target_id)
   end
 
   def commands_target_type
diff --git a/app/services/projects/autocomplete_service.rb b/app/services/projects/autocomplete_service.rb
index 10eb2cea4a2..5286b92ab6b 100644
--- a/app/services/projects/autocomplete_service.rb
+++ b/app/services/projects/autocomplete_service.rb
@@ -47,15 +47,7 @@ module Projects
     end
 
     def commands(noteable, type)
-      noteable ||=
-        case type
-        when 'Issue'
-          @project.issues.build
-        when 'MergeRequest'
-          @project.merge_requests.build
-        end
-
-      return [] unless noteable&.is_a?(Issuable)
+      return [] unless noteable
 
       QuickActions::InterpretService.new(project, current_user).available_commands(noteable)
     end
diff --git a/app/services/quick_actions/interpret_service.rb b/app/services/quick_actions/interpret_service.rb
index cdc8514c47c..8838ed06324 100644
--- a/app/services/quick_actions/interpret_service.rb
+++ b/app/services/quick_actions/interpret_service.rb
@@ -60,7 +60,8 @@ module QuickActions
       "Closes this #{issuable.to_ability_name.humanize(capitalize: false)}."
     end
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         issuable.open? &&
         current_user.can?(:"update_#{issuable.to_ability_name}", issuable)
     end
@@ -75,7 +76,8 @@ module QuickActions
       "Reopens this #{issuable.to_ability_name.humanize(capitalize: false)}."
     end
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         issuable.closed? &&
         current_user.can?(:"update_#{issuable.to_ability_name}", issuable)
     end
@@ -149,7 +151,8 @@ module QuickActions
       issuable.allows_multiple_assignees? ? '@user1 @user2' : ''
     end
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         issuable.assignees.any? &&
         current_user.can?(:"admin_#{issuable.to_ability_name}", project)
     end
@@ -188,7 +191,8 @@ module QuickActions
       "Removes #{issuable.milestone.to_reference(format: :name)} milestone."
     end
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         issuable.milestone_id? &&
         current_user.can?(:"admin_#{issuable.to_ability_name}", project)
     end
@@ -231,7 +235,8 @@ module QuickActions
     end
     params '~label1 ~"label 2"'
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         issuable.labels.any? &&
         current_user.can?(:"admin_#{issuable.to_ability_name}", project)
     end
@@ -257,7 +262,8 @@ module QuickActions
     end
     params '~label1 ~"label 2"'
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         issuable.labels.any? &&
         current_user.can?(:"admin_#{issuable.to_ability_name}", project)
     end
@@ -295,7 +301,8 @@ module QuickActions
     desc 'Add a todo'
     explanation 'Adds a todo.'
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         !TodoService.new.todo_exist?(issuable, current_user)
     end
     command :todo do
@@ -317,7 +324,8 @@ module QuickActions
       "Subscribes to this #{issuable.to_ability_name.humanize(capitalize: false)}."
     end
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         !issuable.subscribed?(current_user, project)
     end
     command :subscribe do
@@ -329,7 +337,8 @@ module QuickActions
       "Unsubscribes from this #{issuable.to_ability_name.humanize(capitalize: false)}."
     end
     condition do
-      issuable.persisted? &&
+      issuable.is_a?(Issuable) &&
+        issuable.persisted? &&
         issuable.subscribed?(current_user, project)
     end
     command :unsubscribe do
@@ -385,7 +394,8 @@ module QuickActions
     end
     params ':emoji:'
     condition do
-      issuable.persisted?
+      issuable.is_a?(Issuable) &&
+        issuable.persisted?
     end
     parse_params do |emoji_param|
       match = emoji_param.match(Banzai::Filter::EmojiFilter.emoji_pattern)
@@ -574,6 +584,23 @@ module QuickActions
       @updates[:confidential] = true
     end
 
+    desc 'Tag this commit.'
+    explanation do |tag_name, message|
+      with_message = %{ with "#{message}"} if message.present?
+      "Tags this commit to #{tag_name}#{with_message}."
+    end
+    params 'v1.2.3 <message>'
+    parse_params do |tag_name_and_message|
+      tag_name_and_message.split(' ', 2)
+    end
+    condition do
+      issuable.is_a?(Commit) && current_user.can?(:push_code, project)
+    end
+    command :tag do |tag_name, message|
+      @updates[:tag_name] = tag_name
+      @updates[:tag_message] = message
+    end
+
     def extract_users(params)
       return [] if params.nil?
 
diff --git a/app/services/quick_actions/target_service.rb b/app/services/quick_actions/target_service.rb
new file mode 100644
index 00000000000..d8ba52c6e50
--- /dev/null
+++ b/app/services/quick_actions/target_service.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module QuickActions
+  class TargetService < BaseService
+    def execute(type, type_id)
+      case type&.downcase
+      when 'issue'
+        issue(type_id)
+      when 'mergerequest'
+        merge_request(type_id)
+      when 'commit'
+        commit(type_id)
+      end
+    end
+
+    private
+
+    def issue(type_id)
+      IssuesFinder.new(current_user, project_id: project.id).find_by(iid: type_id) || project.issues.build
+    end
+
+    def merge_request(type_id)
+      MergeRequestsFinder.new(current_user, project_id: project.id).find_by(iid: type_id) || project.merge_requests.build
+    end
+
+    def commit(type_id)
+      project.commit(type_id)
+    end
+  end
+end
diff --git a/app/services/system_note_service.rb b/app/services/system_note_service.rb
index 77494295f14..dda89830179 100644
--- a/app/services/system_note_service.rb
+++ b/app/services/system_note_service.rb
@@ -32,6 +32,21 @@ module SystemNoteService
     create_note(NoteSummary.new(noteable, project, author, body, action: 'commit', commit_count: total_count))
   end
 
+  # Called when a commit was tagged
+  #
+  # noteable  - Noteable object
+  # project   - Project owning noteable
+  # author    - User performing the tag
+  # tag_name  - The created tag name
+  #
+  # Returns the created Note object
+  def tag_commit(noteable, project, author, tag_name)
+    link = url_helpers.project_tag_url(project, id: tag_name)
+    body = "tagged commit #{noteable.sha} to [`#{tag_name}`](#{link})"
+
+    create_note(NoteSummary.new(noteable, project, author, body, action: 'tag'))
+  end
+
   # Called when the assignee of a Noteable is changed or removed
   #
   # noteable - Noteable object
diff --git a/app/services/tags/create_service.rb b/app/services/tags/create_service.rb
index 329722df747..35390f5082c 100644
--- a/app/services/tags/create_service.rb
+++ b/app/services/tags/create_service.rb
@@ -7,7 +7,7 @@ module Tags
       return error('Tag name invalid') unless valid_tag
 
       repository = project.repository
-      message&.strip!
+      message = message&.strip
 
       new_tag = nil
 
diff --git a/changelogs/unreleased/45663-tag-quick-action-on-commit-comments.yml b/changelogs/unreleased/45663-tag-quick-action-on-commit-comments.yml
new file mode 100644
index 00000000000..6d664511e6e
--- /dev/null
+++ b/changelogs/unreleased/45663-tag-quick-action-on-commit-comments.yml
@@ -0,0 +1,5 @@
+---
+title: "`/tag` quick action on Commit comments"
+merge_request: 20694
+author: Peter Leitzen
+type: added
diff --git a/doc/user/project/quick_actions.md b/doc/user/project/quick_actions.md
index 0ef8eddad20..8fdfd2a6f4d 100644
--- a/doc/user/project/quick_actions.md
+++ b/doc/user/project/quick_actions.md
@@ -1,7 +1,7 @@
 # GitLab quick actions
 
-Quick actions are textual shortcuts for common actions on issues or merge
-requests that are usually done by clicking buttons or dropdowns in GitLab's UI.
+Quick actions are textual shortcuts for common actions on issues, merge requests
+or commits 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
@@ -39,7 +39,8 @@ do.
 | `/board_move ~column`      | Move issue to column on the board |
 | `/duplicate #issue`        | Closes this issue and marks it as a duplicate of another issue |
 | `/move path/to/project`        | Moves issue to another project |
+| `/tag v1.2.3 <message>`    | Tags a commit with a given tag name and optional message |
 | `/tableflip`               | Append the comment with `(╯°□°)╯︵ ┻━┻` |
 | `/shrug`                   | Append the comment with `¯\＿(ツ)＿/¯` |
 | <code>/copy_metadata #issue &#124; !merge_request</code> | Copy labels and milestone from other issue or merge request |
-| `/confidential`            | Makes the issue confidential |
\ No newline at end of file
+| `/confidential`            | Makes the issue confidential |
diff --git a/spec/features/commits/user_uses_slash_commands_spec.rb b/spec/features/commits/user_uses_slash_commands_spec.rb
new file mode 100644
index 00000000000..9a4b7bd2444
--- /dev/null
+++ b/spec/features/commits/user_uses_slash_commands_spec.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'Commit > User uses quick actions', :js do
+  include Spec::Support::Helpers::Features::NotesHelpers
+  include RepoHelpers
+
+  let(:project) { create(:project, :public, :repository) }
+  let(:user) { project.creator }
+  let(:commit) { project.commit }
+
+  before do
+    project.add_maintainer(user)
+    sign_in(user)
+
+    visit project_commit_path(project, commit.id)
+  end
+
+  describe 'Tagging a commit' do
+    let(:tag_name) { 'v1.2.3' }
+    let(:tag_message) { 'Stable release' }
+    let(:truncated_commit_sha) { Commit.truncate_sha(commit.sha) }
+
+    it 'tags this commit' do
+      add_note("/tag #{tag_name} #{tag_message}")
+
+      expect(page).to have_content 'Commands applied'
+      expect(page).to have_content "tagged commit #{truncated_commit_sha}"
+      expect(page).to have_content tag_name
+
+      visit project_tag_path(project, tag_name)
+      expect(page).to have_content tag_name
+      expect(page).to have_content tag_message
+      expect(page).to have_content truncated_commit_sha
+    end
+
+    describe 'preview', :js do
+      it 'removes quick action from note and explains it' do
+        preview_note("/tag #{tag_name} #{tag_message}")
+
+        expect(page).not_to have_content '/tag'
+        expect(page).to have_content %{Tags this commit to #{tag_name} with "#{tag_message}"}
+        expect(page).to have_content tag_name
+      end
+    end
+  end
+end
diff --git a/spec/services/commits/tag_service_spec.rb b/spec/services/commits/tag_service_spec.rb
new file mode 100644
index 00000000000..82377a8dace
--- /dev/null
+++ b/spec/services/commits/tag_service_spec.rb
@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Commits::TagService do
+  let(:project) { create(:project, :repository) }
+  let(:user) { create(:user) }
+
+  let(:commit) { project.commit }
+
+  before do
+    project.add_maintainer(user)
+  end
+
+  describe '#execute' do
+    let(:service) { described_class.new(project, user, opts) }
+
+    shared_examples 'tag failure' do
+      it 'returns a hash with the :error status' do
+        result = service.execute(commit)
+
+        expect(result[:status]).to eq(:error)
+        expect(result[:message]).to eq(error_message)
+      end
+
+      it 'does not add a system note' do
+        service.execute(commit)
+
+        description_notes = find_notes('tag')
+        expect(description_notes).to be_empty
+      end
+    end
+
+    def find_notes(action)
+      commit
+        .notes
+        .joins(:system_note_metadata)
+        .where(system_note_metadata: { action: action })
+    end
+
+    context 'valid params' do
+      let(:opts) do
+        {
+          tag_name: 'v1.2.3',
+          tag_message: 'Release'
+        }
+      end
+
+      def find_notes(action)
+        commit
+          .notes
+          .joins(:system_note_metadata)
+          .where(system_note_metadata: { action: action })
+      end
+
+      context 'when tagging succeeds' do
+        it 'returns a hash with the :success status and created tag' do
+          result = service.execute(commit)
+
+          expect(result[:status]).to eq(:success)
+
+          tag = result[:tag]
+          expect(tag.name).to eq(opts[:tag_name])
+          expect(tag.message).to eq(opts[:tag_message])
+        end
+
+        it 'adds a system note' do
+          service.execute(commit)
+
+          description_notes = find_notes('tag')
+          expect(description_notes.length).to eq(1)
+        end
+      end
+
+      context 'when tagging fails' do
+        let(:tag_error) { 'GitLab: You are not allowed to push code to this project.' }
+
+        before do
+          tag_stub = instance_double(Tags::CreateService)
+          allow(Tags::CreateService).to receive(:new).and_return(tag_stub)
+          allow(tag_stub).to receive(:execute).and_return({
+            status: :error, message: tag_error
+          })
+        end
+
+        it_behaves_like 'tag failure' do
+          let(:error_message) { tag_error }
+        end
+      end
+    end
+
+    context 'invalid params' do
+      let(:opts) do
+        {}
+      end
+
+      it_behaves_like 'tag failure' do
+        let(:error_message) { 'Missing parameter tag_name' }
+      end
+    end
+  end
+end
diff --git a/spec/services/notes/quick_actions_service_spec.rb b/spec/services/notes/quick_actions_service_spec.rb
index 784dac55454..a8c994c101c 100644
--- a/spec/services/notes/quick_actions_service_spec.rb
+++ b/spec/services/notes/quick_actions_service_spec.rb
@@ -11,40 +11,6 @@ describe Notes::QuickActionsService do
     end
   end
 
-  shared_examples 'note on noteable that does not support quick actions' 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 quick actions' do
     include_context 'note on noteable'
 
@@ -147,16 +113,16 @@ describe Notes::QuickActionsService do
       expect(described_class.noteable_update_service(note)).to eq(Issues::UpdateService)
     end
 
-    it 'returns Issues::UpdateService for a note on a merge request' do
+    it 'returns MergeRequests::UpdateService for a note on a merge request' do
       note = create(:note_on_merge_request, project: project)
 
       expect(described_class.noteable_update_service(note)).to eq(MergeRequests::UpdateService)
     end
 
-    it 'returns nil for a note on a commit' do
+    it 'returns Commits::TagService for a note on a commit' do
       note = create(:note_on_commit, project: project)
 
-      expect(described_class.noteable_update_service(note)).to be_nil
+      expect(described_class.noteable_update_service(note)).to eq(Commits::TagService)
     end
   end
 
@@ -175,7 +141,7 @@ describe Notes::QuickActionsService do
       let(:note) { create(:note_on_commit, project: project) }
 
       it 'returns false' do
-        expect(described_class.supported?(note)).to be_falsy
+        expect(described_class.supported?(note)).to be_truthy
       end
     end
   end
@@ -203,10 +169,6 @@ describe Notes::QuickActionsService do
     it_behaves_like 'note on noteable that supports quick actions' do
       let(:note) { build(:note_on_merge_request, project: project) }
     end
-
-    it_behaves_like 'note on noteable that does not support quick actions' do
-      let(:note) { build(:note_on_commit, project: project) }
-    end
   end
 
   context 'CE restriction for issue assignees' do
diff --git a/spec/services/preview_markdown_service_spec.rb b/spec/services/preview_markdown_service_spec.rb
index 81dc7c57f4a..507909d9231 100644
--- a/spec/services/preview_markdown_service_spec.rb
+++ b/spec/services/preview_markdown_service_spec.rb
@@ -65,6 +65,31 @@ describe PreviewMarkdownService do
     end
   end
 
+  context 'commit description' do
+    let(:project) { create(:project, :repository) }
+    let(:commit) { project.commit }
+    let(:params) do
+      {
+        text: "My work\n/tag v1.2.3 Stable release",
+        quick_actions_target_type: 'Commit',
+        quick_actions_target_id: commit.id
+      }
+    end
+    let(:service) { described_class.new(project, user, params) }
+
+    it 'removes quick actions from text' do
+      result = service.execute
+
+      expect(result[:text]).to eq 'My work'
+    end
+
+    it 'explains quick actions effect' do
+      result = service.execute
+
+      expect(result[:commands]).to eq 'Tags this commit to v1.2.3 with "Stable release".'
+    end
+  end
+
   it 'sets correct markdown engine' do
     service = described_class.new(project, user, { markdown_version: CacheMarkdownField::CACHE_REDCARPET_VERSION })
     result  = service.execute
diff --git a/spec/services/quick_actions/interpret_service_spec.rb b/spec/services/quick_actions/interpret_service_spec.rb
index 743e281183e..bf1c157c4a2 100644
--- a/spec/services/quick_actions/interpret_service_spec.rb
+++ b/spec/services/quick_actions/interpret_service_spec.rb
@@ -6,6 +6,7 @@ describe QuickActions::InterpretService do
   let(:developer2) { create(:user) }
   let(:issue) { create(:issue, project: project) }
   let(:milestone) { create(:milestone, project: project, title: '9.10') }
+  let(:commit) { create(:commit, project: project) }
   let(:inprogress) { create(:label, project: project, title: 'In Progress') }
   let(:bug) { create(:label, project: project, title: 'Bug') }
   let(:note) { build(:note, commit_id: merge_request.diff_head_sha) }
@@ -347,6 +348,14 @@ describe QuickActions::InterpretService do
       end
     end
 
+    shared_examples 'tag command' do
+      it 'tags a commit' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(tag_name: tag_name, tag_message: tag_message)
+      end
+    end
+
     it_behaves_like 'reopen command' do
       let(:content) { '/reopen' }
       let(:issuable) { issue }
@@ -628,16 +637,6 @@ describe QuickActions::InterpretService do
       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 }
@@ -787,6 +786,28 @@ describe QuickActions::InterpretService do
       let(:issuable) { issue }
     end
 
+    context '/todo' do
+      let(:content) { '/todo' }
+
+      context 'if issuable is an Issue' do
+        it_behaves_like 'todo command' do
+          let(:issuable) { issue }
+        end
+      end
+
+      context 'if issuable is a MergeRequest' do
+        it_behaves_like 'todo command' do
+          let(:issuable) { merge_request }
+        end
+      end
+
+      context 'if issuable is a Commit' do
+        it_behaves_like 'empty command' do
+          let(:issuable) { commit }
+        end
+      end
+    end
+
     context '/copy_metadata command' do
       let(:todo_label) { create(:label, project: project, title: 'To Do') }
       let(:inreview_label) { create(:label, project: project, title: 'In Review') }
@@ -971,6 +992,12 @@ describe QuickActions::InterpretService do
           let(:issuable) { issue }
         end
       end
+
+      context 'if issuable is a Commit' do
+        let(:content) { '/award :100:' }
+        let(:issuable) { commit }
+        it_behaves_like 'empty command'
+      end
     end
 
     context '/shrug command' do
@@ -1102,6 +1129,32 @@ describe QuickActions::InterpretService do
         it_behaves_like 'empty command'
       end
     end
+
+    context '/tag command' do
+      let(:issuable) { commit }
+
+      context 'ignores command with no argument' do
+        it_behaves_like 'empty command' do
+          let(:content) { '/tag' }
+        end
+      end
+
+      context 'tags a commit with a tag name' do
+        it_behaves_like 'tag command' do
+          let(:tag_name) { 'v1.2.3' }
+          let(:tag_message) { nil }
+          let(:content) { "/tag #{tag_name}" }
+        end
+      end
+
+      context 'tags a commit with a tag name and message' do
+        it_behaves_like 'tag command' do
+          let(:tag_name) { 'v1.2.3' }
+          let(:tag_message) { 'Stable release' }
+          let(:content) { "/tag #{tag_name} #{tag_message}" }
+        end
+      end
+    end
   end
 
   describe '#explain' do
@@ -1319,5 +1372,39 @@ describe QuickActions::InterpretService do
         expect(explanations).to eq(["Moves this issue to test/project."])
       end
     end
+
+    describe 'tag a commit' do
+      describe 'with a tag name' do
+        context 'without a message' do
+          let(:content) { '/tag v1.2.3' }
+
+          it 'includes the tag name only' do
+            _, explanations = service.explain(content, commit)
+
+            expect(explanations).to eq(["Tags this commit to v1.2.3."])
+          end
+        end
+
+        context 'with an empty message' do
+          let(:content) { '/tag v1.2.3 ' }
+
+          it 'includes the tag name only' do
+            _, explanations = service.explain(content, commit)
+
+            expect(explanations).to eq(["Tags this commit to v1.2.3."])
+          end
+        end
+      end
+
+      describe 'with a tag name and message' do
+        let(:content) { '/tag v1.2.3 Stable release' }
+
+        it 'includes the tag name and message' do
+          _, explanations = service.explain(content, commit)
+
+          expect(explanations).to eq(["Tags this commit to v1.2.3 with \"Stable release\"."])
+        end
+      end
+    end
   end
 end
diff --git a/spec/services/quick_actions/target_service_spec.rb b/spec/services/quick_actions/target_service_spec.rb
new file mode 100644
index 00000000000..0aeb29cbeec
--- /dev/null
+++ b/spec/services/quick_actions/target_service_spec.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe QuickActions::TargetService do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:service) { described_class.new(project, user) }
+
+  before do
+    project.add_maintainer(user)
+  end
+
+  describe '#execute' do
+    shared_examples 'no target' do |type_id:|
+      it 'returns nil' do
+        target = service.execute(type, type_id)
+
+        expect(target).to be_nil
+      end
+    end
+
+    shared_examples 'find target' do
+      it 'returns the target' do
+        found_target = service.execute(type, target_id)
+
+        expect(found_target).to eq(target)
+      end
+    end
+
+    shared_examples 'build target' do |type_id:|
+      it 'builds a new target' do
+        target = service.execute(type, type_id)
+
+        expect(target.project).to eq(project)
+        expect(target).to be_new_record
+      end
+    end
+
+    context 'for issue' do
+      let(:target) { create(:issue, project: project) }
+      let(:target_id) { target.iid }
+      let(:type) { 'Issue' }
+
+      it_behaves_like 'find target'
+      it_behaves_like 'build target', type_id: nil
+      it_behaves_like 'build target', type_id: -1
+    end
+
+    context 'for merge request' do
+      let(:target) { create(:merge_request, source_project: project) }
+      let(:target_id) { target.iid }
+      let(:type) { 'MergeRequest' }
+
+      it_behaves_like 'find target'
+      it_behaves_like 'build target', type_id: nil
+      it_behaves_like 'build target', type_id: -1
+    end
+
+    context 'for commit' do
+      let(:project) { create(:project, :repository) }
+      let(:target) { project.commit.parent }
+      let(:target_id) { target.sha }
+      let(:type) { 'Commit' }
+
+      it_behaves_like 'find target'
+      it_behaves_like 'no target', type_id: 'invalid_sha'
+
+      context 'with nil target_id' do
+        let(:target) { project.commit }
+        let(:target_id) { nil }
+
+        it_behaves_like 'find target'
+      end
+    end
+
+    context 'for unknown type' do
+      let(:type) { 'unknown' }
+
+      it_behaves_like 'no target', type_id: :unused
+    end
+  end
+end
diff --git a/spec/services/system_note_service_spec.rb b/spec/services/system_note_service_spec.rb
index 57d081cffb3..442de61f69b 100644
--- a/spec/services/system_note_service_spec.rb
+++ b/spec/services/system_note_service_spec.rb
@@ -108,6 +108,25 @@ describe SystemNoteService do
     end
   end
 
+  describe '.tag_commit' do
+    let(:noteable) do
+      project.commit
+    end
+    let(:tag_name) { 'v1.2.3' }
+
+    subject { described_class.tag_commit(noteable, project, author, tag_name) }
+
+    it_behaves_like 'a system note' do
+      let(:action) { 'tag' }
+    end
+
+    it 'sets the note text' do
+      link = "http://localhost/#{project.full_path}/tags/#{tag_name}"
+
+      expect(subject.note).to eq "tagged commit #{noteable.sha} to [`#{tag_name}`](#{link})"
+    end
+  end
+
   describe '.change_assignee' do
     subject { described_class.change_assignee(noteable, project, author, assignee) }
 
diff --git a/spec/support/helpers/features/notes_helpers.rb b/spec/support/helpers/features/notes_helpers.rb
index 2b9f8b30c60..89517fde6e2 100644
--- a/spec/support/helpers/features/notes_helpers.rb
+++ b/spec/support/helpers/features/notes_helpers.rb
@@ -20,6 +20,13 @@ module Spec
               end
             end
           end
+
+          def preview_note(text)
+            page.within('.js-main-target-form') do
+              fill_in('note[note]', with: text)
+              click_on('Preview')
+            end
+          end
         end
       end
     end
diff --git a/spec/views/shared/notes/_form.html.haml_spec.rb b/spec/views/shared/notes/_form.html.haml_spec.rb
index c57319869f3..0189f926a5f 100644
--- a/spec/views/shared/notes/_form.html.haml_spec.rb
+++ b/spec/views/shared/notes/_form.html.haml_spec.rb
@@ -16,7 +16,7 @@ describe 'shared/notes/_form' do
     render
   end
 
-  %w[issue merge_request].each do |noteable|
+  %w[issue merge_request commit].each do |noteable|
     context "with a note on #{noteable}" do
       let(:note) { build(:"note_on_#{noteable}", project: project) }
 
@@ -25,12 +25,4 @@ describe 'shared/notes/_form' do
       end
     end
   end
-
-  context 'with a note on a commit' do
-    let(:note) { build(:note_on_commit, project: project) }
-
-    it 'says that only markdown is supported, not quick actions' do
-      expect(rendered).to have_content('Markdown is supported')
-    end
-  end
 end