Merge branch '28682-can-merge-branch-before-build-is-started' into 'master'

Resolve "Can merge branch before build is started"

Closes #28682

See merge request gitlab-org/gitlab-ce!22911

app/models/merge_request.rb

@@ -966,7 +966,6 @@ class MergeRequest < ActiveRecord::Base
   def mergeable_ci_state?
     return true unless project.only_allow_merge_if_pipeline_succeeds?
-    return true unless head_pipeline
     actual_head_pipeline&.success? || actual_head_pipeline&.skipped?
   end

changelogs/unreleased/28682-can-merge-branch-before-build-is-started.yml

+---
+title: Strictly require a pipeline to merge.
+merge_request: 22911
+author:
+type: changed

spec/models/merge_request_spec.rb

@@ -1782,7 +1782,7 @@ describe MergeRequest do
           allow(subject).to receive(:head_pipeline) { nil }
         end
-        it { expect(subject.mergeable_ci_state?).to be_truthy }
+        it { expect(subject.mergeable_ci_state?).to be_falsey }
       end
     end