Merge branch '59257-find-new-branches-harder' into 'master'

Look for new branches more carefully

Closes #59257

See merge request gitlab-org/gitlab-ce!29761

app/services/git/branch_hooks_service.rb

@@ -105,8 +105,14 @@ module Git
       CreateGpgSignatureWorker.perform_async(signable, project.id)
     end
 
+    # It's not sufficient to just check for a blank SHA as it's possible for the
+    # branch to be pushed, but for the `post-receive` hook to never run:
+    # https://gitlab.com/gitlab-org/gitlab-ce/issues/59257
     def creating_branch?
-      Gitlab::Git.blank_ref?(params[:oldrev])
+      strong_memoize(:creating_branch) do
+        Gitlab::Git.blank_ref?(params[:oldrev]) ||
+          !project.repository.branch_exists?(branch_name)
+      end
     end
 
     def updating_branch?

changelogs/unreleased/59257-find-new-branches-harder.yml

+---
+title: Look for new branches more carefully
+merge_request: 29761
+author:
+type: fixed

spec/services/git/branch_hooks_service_spec.rb

@@ -344,4 +344,38 @@ describe Git::BranchHooksService do
       end
     end
   end
+
+  describe 'New branch detection' do
+    let(:branch) { 'fix' }
+
+    context 'oldrev is the blank SHA' do
+      let(:oldrev) { Gitlab::Git::BLANK_SHA }
+
+      it 'is treated as a new branch' do
+        expect(service).to receive(:branch_create_hooks)
+
+        service.execute
+      end
+    end
+
+    context 'oldrev is set' do
+      context 'Gitaly does not know about the branch' do
+        it 'is treated as a new branch' do
+          allow(project.repository).to receive(:branch_names) { [] }
+
+          expect(service).to receive(:branch_create_hooks)
+
+          service.execute
+        end
+      end
+
+      context 'Gitaly knows about the branch' do
+        it 'is not treated as a new branch' do
+          expect(service).not_to receive(:branch_create_hooks)
+
+          service.execute
+        end
+      end
+    end
+  end
 end