Add squash commit template field in project settings and docs

This change allows editing project's squash_commit_template
in project settings. Additionally it adds documentation
on squash commit template feature.

app/views/projects/_merge_request_settings.html.haml

@@ -12,5 +12,7 @@
 
 = render 'projects/merge_request_merge_commit_template', project: @project, form: form
 
+= render 'projects/merge_request_squash_commit_template', project: @project, form: form
+
 - if @project.forked?
   = render 'projects/merge_request_target_project_settings', project: @project, form: form

app/views/projects/_merge_request_squash_commit_template.html.haml

+- form = local_assigns.fetch(:form)
+
+.form-group
+  %b= s_('ProjectSettings|Squash commit message template')
+  %p.text-secondary
+    - configure_the_squash_commit_message_help_link_url = help_page_path('user/project/merge_requests/commit_templates.md', anchor: 'squash-commit-message-template')
+    - configure_the_squash_commit_message_help_link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: configure_the_squash_commit_message_help_link_url }
+    = s_('ProjectSettings|The commit message used when squashing commits. %{link_start}Learn more about syntax and variables.%{link_end}').html_safe % { link_start: configure_the_squash_commit_message_help_link_start, link_end: '</a>'.html_safe }
+  .mb-2
+    = form.text_area :squash_commit_template, class: 'form-control gl-form-input', rows: 8, maxlength: 500, placeholder: '%{title}'
+    %p.form-text.text-muted
+      = s_('ProjectSettings|Maximum 500 characters.')
+      = s_('ProjectSettings|Supported variables:')
+      - Gitlab::MergeRequests::CommitMessageGenerator::PLACEHOLDERS.keys.each do |placeholder|
+        %code
+          = "%{#{placeholder}}".html_safe

doc/user/project/merge_requests/commit_templates.md

@@ -31,7 +31,7 @@ This commit message can be customized to follow any guidelines you might have.
 To do so, expand the **Merge requests** tab within your project's **General**
 settings and change the **Merge commit message template** text:
 
-![Custom commit message for applied suggestions](img/merge_commit_message_template_v14_5.png)
+![Custom commit message for merge commit](img/merge_commit_message_template_v14_5.png)
 
 You can use static text and following variables:
 
@@ -49,3 +49,18 @@ Empty variables that are the only word in a line will be removed along with all
 
 Merge commit template field has a limit of 500 characters. This limit only applies to the template
 itself.
+
+## Squash commit message template
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/345275) in GitLab 14.6.
+
+As a project maintainer, you're able to configure squash commit message template. It will be used during merge with
+squash to create squash commit message. It uses the same syntax and variables as merge commit message template.
+
+![Custom commit message for squash commit](img/squash_commit_message_template_v14_6.png)
+
+Default squash commit message can be recreated using following template:
+
+```plaintext
+%{title}
+```

doc/user/project/merge_requests/squash_and_merge.md

@@ -28,9 +28,9 @@ NOTE:
 The squashed commit in this example is followed by a merge commit, because the merge method for this repository uses a merge commit. You can disable merge commits in
 **Project Settings > General > Merge requests > Merge method > Fast-forward merge**.
 
-The squashed commit's default commit message is taken from the merge request title.
+The squashed commit's default commit message is taken from the merge request title. It can be changed using [squash commit message template](commit_templates.md#squash-commit-message-template).
 
-It can be customized before merging a merge request.
+It can also be customized before merging a merge request.
 
 ![A squash commit message editor](img/squash_mr_message.png)
 

doc/user/project/settings/index.md

@@ -315,7 +315,7 @@ Set up your project's merge request settings:
 - Enable [require an associated issue from Jira](../../../integration/jira/issues.md#require-associated-jira-issue-for-merge-requests-to-be-merged).
 - Enable [`delete source branch after merge` option by default](../merge_requests/getting_started.md#deleting-the-source-branch).
 - Configure [suggested changes commit messages](../merge_requests/reviews/suggestions.md#configure-the-commit-message-for-applied-suggestions).
-- Configure [merge commit message template](../merge_requests/commit_templates.md).
+- Configure [merge and squash commit message templates](../merge_requests/commit_templates.md).
 - Configure [the default target project](../merge_requests/creating_merge_requests.md#set-the-default-target-project) for merge requests coming from forks.
 
 ### Service Desk

ee/app/views/projects/_merge_request_settings.html.haml

@@ -15,6 +15,8 @@
 
 = render_ce 'projects/merge_request_merge_commit_template', project: @project, form: form
 
+= render_ce 'projects/merge_request_squash_commit_template', project: @project, form: form
+
 - if @project.forked?
   = render_ce 'projects/merge_request_target_project_settings', project: @project, form: form
 

locale/gitlab.pot

@@ -27407,6 +27407,9 @@ msgstr ""
 msgid "ProjectSettings|Snippets"
 msgstr ""
 
+msgid "ProjectSettings|Squash commit message template"
+msgstr ""
+
 msgid "ProjectSettings|Squash commits when merging"
 msgstr ""
 
@@ -27431,6 +27434,9 @@ msgstr ""
 msgid "ProjectSettings|The commit message used when merging, if the merge method creates a merge commit. %{link_start}Learn more about syntax and variables.%{link_end}"
 msgstr ""
 
+msgid "ProjectSettings|The commit message used when squashing commits. %{link_start}Learn more about syntax and variables.%{link_end}"
+msgstr ""
+
 msgid "ProjectSettings|The default target project for merge requests created in this fork project."
 msgstr ""
 

spec/views/projects/edit.html.haml_spec.rb

@@ -92,6 +92,22 @@ RSpec.describe 'projects/edit' do
     end
   end
 
+  context 'squash template' do
+    it 'displays a placeholder if none is set' do
+      render
+
+      expect(rendered).to have_field('project[squash_commit_template]', placeholder: '%{title}')
+    end
+
+    it 'displays the user entered value' do
+      project.update!(squash_commit_template: '%{first_multiline_commit}')
+
+      render
+
+      expect(rendered).to have_field('project[squash_commit_template]', with: '%{first_multiline_commit}')
+    end
+  end
+
   context 'forking' do
     before do
       assign(:project, project)