3 files changed, 66 insertions, 0 deletions
diff --git a/app/services/merge_requests/cleanup_refs_service.rb b/app/services/merge_requests/cleanup_refs_service.rb
new file mode 100644
index 00000000000..e34d568cdcd
--- /dev/null
+++ b/app/services/merge_requests/cleanup_refs_service.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+module MergeRequests
+  class CleanupRefsService
+    include BaseServiceUtility
+
+    TIME_THRESHOLD = 14.days
+
+    attr_reader :merge_request
+
+    def self.schedule(merge_request)
+      MergeRequestCleanupRefsWorker.perform_in(TIME_THRESHOLD, merge_request.id)
+    end
+
+    def initialize(merge_request)
+      @merge_request = merge_request
+      @repository = merge_request.project.repository
+      @ref_path = merge_request.ref_path
+      @ref_head_sha = @repository.commit(merge_request.ref_path).id
+    end
+
+    def execute
+      return error("Merge request has not been closed nor merged for #{TIME_THRESHOLD.inspect}.") unless eligible?
+
+      # Ensure that commit shas of refs are kept around so we won't lose them when GC runs.
+      keep_around
+
+      return error('Failed to create keep around refs.') unless kept_around?
+
+      delete_refs
+      success
+    end
+
+    private
+
+    attr_reader :repository, :ref_path, :ref_head_sha
+
+    def eligible?
+      return met_time_threshold?(merge_request.metrics&.latest_closed_at) if merge_request.closed?
+
+      merge_request.merged? && met_time_threshold?(merge_request.metrics&.merged_at)
+    end
+
+    def met_time_threshold?(attr)
+      attr.nil? || attr.to_i <= TIME_THRESHOLD.ago.to_i
+    end
+
+    def kept_around?
+      Gitlab::Git::KeepAround.new(repository).kept_around?(ref_head_sha)
+    end
+
+    def keep_around
+      repository.keep_around(ref_head_sha)
+    end
+
+    def delete_refs
+      repository.delete_refs(ref_path)
+    end
+  end
+end
diff --git a/app/services/merge_requests/close_service.rb b/app/services/merge_requests/close_service.rb
index c2174d2a130..b0a7face594 100644
--- a/app/services/merge_requests/close_service.rb
+++ b/app/services/merge_requests/close_service.rb
@@ -2,6 +2,8 @@
 
 module MergeRequests
   class CloseService < MergeRequests::BaseService
+    include RemovesRefs
+
     def execute(merge_request, commit = nil)
       return merge_request unless can?(current_user, :update_merge_request, merge_request)
 
@@ -19,6 +21,7 @@ module MergeRequests
         merge_request.update_project_counter_caches
         cleanup_environments(merge_request)
         abort_auto_merge(merge_request, 'merge request was closed')
+        cleanup_refs(merge_request)
       end
 
       merge_request
diff --git a/app/services/merge_requests/post_merge_service.rb b/app/services/merge_requests/post_merge_service.rb
index fdf8f442297..1c78fca3c26 100644
--- a/app/services/merge_requests/post_merge_service.rb
+++ b/app/services/merge_requests/post_merge_service.rb
@@ -7,6 +7,8 @@ module MergeRequests
   # and execute all hooks and notifications
   #
   class PostMergeService < MergeRequests::BaseService
+    include RemovesRefs
+
     def execute(merge_request)
       merge_request.mark_as_merged
       close_issues(merge_request)
@@ -20,6 +22,7 @@ module MergeRequests
       delete_non_latest_diffs(merge_request)
       cancel_review_app_jobs!(merge_request)
       cleanup_environments(merge_request)
+      cleanup_refs(merge_request)
     end
 
     private