Support short reference to group entities from project entities

- add a direct project parent (group) to Banzai context
- if an epic is referenced from a direct descendant
  -> change epic to_reference to use short reference

doc/user/project/quick_actions.md

 # GitLab quick actions
 
-Quick actions are textual shortcuts for common actions on issues, epics, merge requests, 
+Quick actions are textual shortcuts for common actions on issues, epics, merge requests,
 and 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, or
-in comments of issues, epics, merge requests, and commits. Each command should be 
+in comments of issues, epics, merge requests, and commits. Each command should be
 on a separate line in order to be properly detected and executed. Once executed,
 the commands are removed from the text body and not visible to anyone else.
 
@@ -42,7 +42,7 @@ discussions, and descriptions:
 | `/remove_due_date`         | Remove due date                | ✓     |               |
 | `/weight 0,1,2, ...`       | Set weight **[STARTER]**       | ✓     |               |
 | `/clear_weight`            | Clears weight **[STARTER]**    | ✓     |               |
-| `/epic <group&epic &#124; Epic URL>` | Add to epic **[ULTIMATE]** | ✓ |             |
+| `/epic <&epic &#124; group&epic &#124; Epic URL>` | Add to epic **[ULTIMATE]** | ✓ |             |
 | `/remove_epic`             | Removes from epic **[ULTIMATE]** | ✓   |               |
 | `/confidential`            | Make confidential              | ✓     |               |
 | `/duplicate #issue`        | Mark this issue as a duplicate of another issue | ✓    |
@@ -68,7 +68,7 @@ The following quick actions are applicable for epics threads and description:
 |:---------------------------|:----------------------------------------|
 | `/tableflip <Comment>`     | Append the comment with `(╯°□°)╯︵ ┻━┻` |
 | `/shrug <Comment>`         | Append the comment with `¯\＿(ツ)＿/¯`  |
-| `/todo`                    | Add a todo                              | 
+| `/todo`                    | Add a todo                              |
 | `/done`                    | Mark todo as done                       |
 | `/subscribe`               | Subscribe                               |
 | `/unsubscribe`             | Unsubscribe                             |
@@ -78,4 +78,4 @@ The following quick actions are applicable for epics threads and description:
 | `/award :emoji:`           | Toggle emoji award                      |
 | `/label ~label1 ~label2`   | Add label(s)                            |
 | `/unlabel ~label1 ~label2` | Remove all or specific label(s)         |
-| `/relabel ~label1 ~label2` | Replace label                           |
\ No newline at end of file
+| `/relabel ~label1 ~label2` | Replace label                           |

ee/app/models/ee/epic.rb

@@ -194,7 +194,7 @@ module EE
     def to_reference(from = nil, full: false)
       reference = "#{self.class.reference_prefix}#{iid}"
 
-      return reference unless cross_reference?(from) || full
+      return reference unless  (cross_reference?(from) && !group.projects.include?(from)) || full
 
       "#{group.full_path}#{reference}"
     end

ee/app/services/ee/quick_actions/interpret_service.rb

@@ -55,7 +55,7 @@ module EE
           issuable.project.group&.feature_available?(:epics) &&
           current_user.can?(:"admin_#{issuable.to_ability_name}", issuable)
       end
-      params '<group&epic | Epic URL>'
+      params '<&epic | group&epic | Epic URL>'
       command :epic do |epic_param|
         @updates[:epic] = extract_epic(epic_param)
       end

ee/changelogs/unreleased/7287-epic-references.yml

+---
+title: Support short reference to epics from project entities
+merge_request: 7475
+author:
+type: changed

ee/spec/features/epics/referencing_epics_spec.rb

@@ -6,55 +6,75 @@ describe 'Referencing Epics', :js do
   let(:epic) { create(:epic, group: group) }
   let(:project) { create(:project, :public) }
 
-  let(:reference) { epic.to_reference(full: true) }
+  let(:full_reference) { epic.to_reference(full: true) }
 
   context 'reference on an issue' do
-    let(:issue) { create(:issue, project: project, description: "Check #{reference}") }
-
     before do
       stub_licensed_features(epics: true)
 
       sign_in(user)
     end
 
-    context 'when non group member displays the issue' do
-      context 'when referenced epic is in a public group' do
-        it 'displays link to the reference' do
-          visit project_issue_path(project, issue)
+    context 'when referencing epics from the direct parent' do
+      let(:epic2) { create(:epic, group: group) }
+      let(:short_reference) { epic2.to_reference }
+      let(:text) { "Check #{full_reference} #{short_reference}" }
+      let(:child_project) { create(:project, :public, group: group) }
+      let(:issue) { create(:issue, project: child_project, description: text) }
 
-          page.within('.issuable-details .description') do
-            expect(page).to have_link(reference, href: group_epic_path(group, epic))
-          end
+      it 'displays link to the reference' do
+        visit project_issue_path(child_project, issue)
+
+        page.within('.issuable-details .description') do
+          expect(page).to have_link(epic.to_reference, href: group_epic_path(group, epic))
+          expect(page).to have_link(short_reference, href: group_epic_path(group, epic2))
         end
       end
+    end
 
-      context 'when referenced epic is in a private group' do
-        before do
-          group.update_attribute(:visibility_level, Gitlab::VisibilityLevel::PRIVATE)
+    context 'when referencing an epic from another group' do
+      let(:text) { "Check #{full_reference}" }
+      let(:issue) { create(:issue, project: project, description: text) }
+
+      context 'when non group member displays the issue' do
+        context 'when referenced epic is in a public group' do
+          it 'displays link to the reference' do
+            visit project_issue_path(project, issue)
+
+            page.within('.issuable-details .description') do
+              expect(page).to have_link(full_reference, href: group_epic_path(group, epic))
+            end
+          end
         end
 
-        it 'does not display link to the reference' do
-          visit project_issue_path(project, issue)
+        context 'when referenced epic is in a private group' do
+          before do
+            group.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+          end
+
+          it 'does not display link to the reference' do
+            visit project_issue_path(project, issue)
 
-          page.within('.issuable-details .description') do
-            expect(page).not_to have_link
+            page.within('.issuable-details .description') do
+              expect(page).not_to have_link
+            end
           end
         end
       end
-    end
 
-    context 'when a group member displays the issue' do
-      context 'when referenced epic is in a private group' do
-        before do
-          group.add_developer(user)
-          group.update_attribute(:visibility_level, Gitlab::VisibilityLevel::PRIVATE)
-        end
+      context 'when a group member displays the issue' do
+        context 'when referenced epic is in a private group' do
+          before do
+            group.add_developer(user)
+            group.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+          end
 
-        it 'displays link to the reference' do
-          visit project_issue_path(project, issue)
+          it 'displays link to the reference' do
+            visit project_issue_path(project, issue)
 
-          page.within('.issuable-details .description') do
-            expect(page).to have_link(reference, href: group_epic_path(group, epic))
+            page.within('.issuable-details .description') do
+              expect(page).to have_link(full_reference, href: group_epic_path(group, epic))
+            end
           end
         end
       end

ee/spec/models/epic_spec.rb

@@ -470,6 +470,10 @@ describe Epic do
 
   describe '#to_reference' do
     let(:group) { create(:group, path: 'group-a') }
+    let(:subgroup) { create(:group) }
+    let(:group_project) { create(:project, group: group) }
+    let(:subgroup_project) { create(:project, group: subgroup) }
+    let(:other_project) { create(:project) }
     let(:epic) { create(:epic, iid: 1, group: group) }
 
     context 'when nil argument' do
@@ -478,23 +482,42 @@ describe Epic do
       end
     end
 
-    context 'when group argument equals epic group' do
+    context 'when from argument equals epic group' do
       it 'returns epic id' do
         expect(epic.to_reference(epic.group)).to eq('&1')
       end
     end
 
-    context 'when group argument differs from epic group' do
+    context 'when from argument is a group different from epic group' do
       it 'returns complete path to the epic' do
         expect(epic.to_reference(create(:group))).to eq('group-a&1')
       end
     end
 
+    context 'when from argument is a project under the epic group' do
+      it 'returns epic id' do
+        expect(epic.to_reference(group_project)).to eq('&1')
+      end
+    end
+
+    context 'when from argument is a project under the epic subgroup' do
+      it 'returns complete path to the epic' do
+        expect(epic.to_reference(subgroup_project)).to eq('group-a&1')
+      end
+    end
+
+    context 'when from argument is a project in another group' do
+      it 'returns complete path to the epic' do
+        expect(epic.to_reference(other_project)).to eq('group-a&1')
+      end
+    end
+
     context 'when full is true' do
       it 'returns complete path to the epic' do
         expect(epic.to_reference(full: true)).to             eq('group-a&1')
         expect(epic.to_reference(epic.group, full: true)).to eq('group-a&1')
         expect(epic.to_reference(group, full: true)).to      eq('group-a&1')
+        expect(epic.to_reference(group_project, full: true)).to eq('group-a&1')
       end
     end
   end

lib/banzai/filter/epic_reference_filter.rb

@@ -11,6 +11,12 @@ module Banzai
       def self.object_class
         Epic
       end
+
+      private
+
+      def group
+        context[:group] || context[:project]&.group
+      end
     end
   end
 end

spec/models/concerns/cache_markdown_field_spec.rb

@@ -331,11 +331,12 @@ describe CacheMarkdownField do
     end
 
     context 'with a project' do
-      let(:thing) { thing_subclass(:project).new(foo: markdown, foo_html: html, project: :project_value) }
+      let(:project) { create(:project, group: create(:group)) }
+      let(:thing) { thing_subclass(:project).new(foo: markdown, foo_html: html, project: project) }
 
       it 'sets the project in the context' do
         is_expected.to have_key(:project)
-        expect(context[:project]).to eq(:project_value)
+        expect(context[:project]).to eq(project)
       end
 
       it 'invalidates the cache when project changes' do