1 files changed, 26 insertions, 0 deletions

diff --git a/app/services/issues/related_branches_service.rb b/app/services/issues/related_branches_service.rb
new file mode 100644
index 00000000000..76af482b7ac
--- /dev/null
+++ b/app/services/issues/related_branches_service.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+# This service fetches all branches containing the current issue's ID, except for
+# those with a merge request open referencing the current issue.
+module Issues
+  class RelatedBranchesService < Issues::BaseService
+    def execute(issue)
+      branches_with_iid_of(issue) - branches_with_merge_request_for(issue)
+    end
+
+    private
+
+    def branches_with_merge_request_for(issue)
+      Issues::ReferencedMergeRequestsService
+        .new(project, current_user)
+        .referenced_merge_requests(issue)
+        .map(&:source_branch)
+    end
+
+    def branches_with_iid_of(issue)
+      project.repository.branch_names.select do |branch|
+        branch =~ /\A#{issue.iid}-(?!\d+-stable)/i
+      end
+    end
+  end
+end