When deleting merged branches, ignore protected tags

In gitlab-org/gitlab-ce!13251 wildcard Protected Branches were handled
properly when deleting all merged branches. But this fix wasn't that
good. It also checked branch names against Protected Tags. That's not
correct.

This change will **only** check if there is a Protected Branch
matching the merged branch, and ignores Protected Tags.

Closes gitlab-org/gitlab-ce#39732.

app/services/delete_merged_branches_service.rb

@@ -13,7 +13,7 @@ class DeleteMergedBranchesService < BaseService
       # Prevent deletion of branches relevant to open merge requests
       branches -= merge_request_branch_names
       # Prevent deletion of protected branches
-      branches = branches.reject { |branch| project.protected_for?(branch) }
+      branches = branches.reject { |branch| ProtectedBranch.protected?(project, branch) }
 
       branches.each do |branch|
         DeleteBranchService.new(project, current_user).execute(branch)

changelogs/unreleased/tc-delete-merged-protected-tags-fix.yml

@@ -0,0 +1,5 @@
+---
+title: When deleting merged branches, ignore protected tags
+merge_request: 15252
+author:
+type: fixed

spec/services/delete_merged_branches_service_spec.rb

@@ -42,6 +42,14 @@ describe DeleteMergedBranchesService do
       expect(project.repository.branch_names).to include('improve/awesome')
     end
 
+    it 'ignores protected tags' do
+      create(:protected_tag, project: project, name: 'improve/*')
+
+      service.execute
+
+      expect(project.repository.branch_names).not_to include('improve/awesome')
+    end
+
     context 'user without rights' do
       let(:user) { create(:user) }