Merge branch 'feature/environment-teardown-when-branch-deleted' into 'master'

Stop environment when branch is deleted

## What does this MR do?

This MR adds a environment teardown service, that is called when user deletes a branch. This most often happens when merge requests is merged.

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing

## What are the relevant issue numbers?

Closes #23218

See merge request !7355

3 files changed, 65 insertions, 6 deletions

diff --git a/app/services/after_branch_delete_service.rb b/app/services/after_branch_delete_service.rb
new file mode 100644
index 00000000000..2be4d3e6ab5
--- /dev/null
+++ b/app/services/after_branch_delete_service.rb
@@ -0,0 +1,23 @@
+require_relative 'base_service'
+
+##
+# Branch can be deleted either by DeleteBranchService
+# or by GitPushService.
+#
+class AfterBranchDeleteService < BaseService
+  attr_reader :branch_name
+
+  def execute(branch_name)
+    @branch_name = branch_name
+
+    stop_environments
+  end
+
+  private
+
+  def stop_environments
+    Ci::StopEnvironmentsService
+      .new(project, current_user)
+      .execute(branch_name)
+  end
+end
diff --git a/app/services/ci/stop_environments_service.rb b/app/services/ci/stop_environments_service.rb
new file mode 100644
index 00000000000..cf590459cb2
--- /dev/null
+++ b/app/services/ci/stop_environments_service.rb
@@ -0,0 +1,29 @@
+module Ci
+  class StopEnvironmentsService < BaseService
+    attr_reader :ref
+
+    def execute(branch_name)
+      @ref = branch_name
+
+      return unless has_ref?
+
+      environments.each do |environment|
+        next unless environment.stoppable?
+        next unless can?(current_user, :create_deployment, project)
+
+        environment.stop!(current_user)
+      end
+    end
+
+    private
+
+    def has_ref?
+      @ref.present?
+    end
+
+    def environments
+      @environments ||= project
+        .environments_recently_updated_on_branch(@ref)
+    end
+  end
+end
diff --git a/app/services/git_push_service.rb b/app/services/git_push_service.rb
index de313095bed..77c6c81cc1b 100644
--- a/app/services/git_push_service.rb
+++ b/app/services/git_push_service.rb
@@ -49,10 +49,7 @@ class GitPushService < BaseService
       update_gitattributes if is_default_branch?
     end
 
-    # Update merge requests that may be affected by this push. A new branch
-    # could cause the last commit of a merge request to change.
-    update_merge_requests
-
+    execute_related_hooks
     perform_housekeeping
   end
 
@@ -62,14 +59,24 @@ class GitPushService < BaseService
 
   protected
 
-  def update_merge_requests
-    UpdateMergeRequestsWorker.perform_async(@project.id, current_user.id, params[:oldrev], params[:newrev], params[:ref])
+  def execute_related_hooks
+    # Update merge requests that may be affected by this push. A new branch
+    # could cause the last commit of a merge request to change.
+    #
+    UpdateMergeRequestsWorker
+      .perform_async(@project.id, current_user.id, params[:oldrev], params[:newrev], params[:ref])
 
     EventCreateService.new.push(@project, current_user, build_push_data)
     @project.execute_hooks(build_push_data.dup, :push_hooks)
     @project.execute_services(build_push_data.dup, :push_hooks)
     Ci::CreatePipelineService.new(@project, current_user, build_push_data).execute
     ProjectCacheWorker.perform_async(@project.id)
+
+    if push_remove_branch?
+      AfterBranchDeleteService
+        .new(project, current_user)
+        .execute(branch_name)
+    end
   end
 
   def perform_housekeeping