3 files changed, 29 insertions, 10 deletions
diff --git a/app/workers/process_commit_worker.rb b/app/workers/process_commit_worker.rb
index d6ed0e253ad..fe6a49976e0 100644
--- a/app/workers/process_commit_worker.rb
+++ b/app/workers/process_commit_worker.rb
@@ -17,6 +17,7 @@ class ProcessCommitWorker
     project = Project.find_by(id: project_id)
 
     return unless project
+    return if commit_exists_in_upstream?(project, commit_hash)
 
     user = User.find_by(id: user_id)
 
@@ -24,8 +25,6 @@ class ProcessCommitWorker
 
     commit = build_commit(project, commit_hash)
 
-    return unless commit.matches_cross_reference_regex?
-
     author = commit.author || user
 
     process_commit_message(project, commit, user, author, default)
@@ -76,4 +75,16 @@ class ProcessCommitWorker
 
     Commit.from_hash(hash, project)
   end
+
+  private
+
+  # Avoid reprocessing commits that already exist in the upstream
+  # when project is forked. This will also prevent duplicated system notes.
+  def commit_exists_in_upstream?(project, commit_hash)
+    return false unless project.forked?
+
+    upstream_project = project.forked_from_project
+    commit_id = commit_hash.with_indifferent_access[:id]
+    upstream_project.commit(commit_id).present?
+  end
 end
diff --git a/changelogs/unreleased/issue_19262.yml b/changelogs/unreleased/issue_19262.yml
new file mode 100644
index 00000000000..7bcbc647fcb
--- /dev/null
+++ b/changelogs/unreleased/issue_19262.yml
@@ -0,0 +1,4 @@
+---
+title: Prevent commits from upstream repositories to be re-processed by forks
+merge_request:
+author:
diff --git a/spec/workers/process_commit_worker_spec.rb b/spec/workers/process_commit_worker_spec.rb
index 6295856b461..4e036285e8c 100644
--- a/spec/workers/process_commit_worker_spec.rb
+++ b/spec/workers/process_commit_worker_spec.rb
@@ -20,14 +20,6 @@ describe ProcessCommitWorker do
       worker.perform(project.id, -1, commit.to_hash)
     end
 
-    it 'does not process the commit when no issues are referenced' do
-      allow(worker).to receive(:build_commit).and_return(double(matches_cross_reference_regex?: false))
-
-      expect(worker).not_to receive(:process_commit_message)
-
-      worker.perform(project.id, user.id, commit.to_hash)
-    end
-
     it 'processes the commit message' do
       expect(worker).to receive(:process_commit_message).and_call_original
 
@@ -39,6 +31,18 @@ describe ProcessCommitWorker do
 
       worker.perform(project.id, user.id, commit.to_hash)
     end
+
+    context 'when commit already exists in upstream project' do
+      let(:forked) { create(:project, :public) }
+
+      it 'does not process commit message' do
+        create(:forked_project_link, forked_to_project: forked, forked_from_project: project)
+
+        expect(worker).not_to receive(:process_commit_message)
+
+        worker.perform(forked.id, user.id, forked.commit.to_hash)
+      end
+    end
   end
 
   describe '#process_commit_message' do