Change default squash commit message to MR title

app/models/merge_request.rb

@@ -1317,11 +1317,8 @@ class MergeRequest < ApplicationRecord
     message.join("\n\n")
   end
 
-  # Returns the oldest multi-line commit message, or the MR title if none found
   def default_squash_commit_message
-    strong_memoize(:default_squash_commit_message) do
-      first_multiline_commit&.safe_message || title
-    end
+    title
   end
 
   # Returns the oldest multi-line commit

doc/user/project/merge_requests/squash_and_merge.md

@@ -30,10 +30,7 @@ NOTE:
 The squashed commit in this example is followed by a merge commit, because the merge method for this repository uses a merge commit. You can disable merge commits in
 **Project Settings > General > Merge requests > Merge method > Fast-forward merge**.
 
-The squashed commit's commit message is either:
-
-- Taken from the first multi-line commit message in the merge.
-- The merge request's title if no multi-line commit message is found.
+The squashed commit's default commit message is taken from the merge request title.
 
 NOTE:
 This only takes effect if there are at least 2 commits. As there is nothing to squash, the commit message does not change if there is only 1 commit.

spec/models/merge_request_spec.rb

@@ -186,39 +186,7 @@ RSpec.describe MergeRequest, factory_default: :keep do
     let(:multiline_commits) { subject.commits.select(&is_multiline) }
     let(:singleline_commits) { subject.commits.reject(&is_multiline) }
 
-    context 'when the total number of commits is safe' do
-      it 'returns the oldest multiline commit message' do
-        expect(subject.default_squash_commit_message).to eq(multiline_commits.last.message)
-      end
-    end
-
-    context 'when the total number of commits is big' do
-      let(:safe_number) { 20 }
-
-      before do
-        stub_const('MergeRequestDiff::COMMITS_SAFE_SIZE', safe_number)
-      end
-
-      it 'returns the oldest multiline commit message from safe number of commits' do
-        expect(subject.default_squash_commit_message).to eq(
-          "remove emtpy file.(beacase git ignore empty file)\nadd whitespace test file.\n"
-        )
-      end
-    end
-
-    it 'returns the merge request title if there are no multiline commits' do
-      expect(subject).to receive(:commits).and_return(
-        CommitCollection.new(project, singleline_commits)
-      )
-
-      expect(subject.default_squash_commit_message).to eq(subject.title)
-    end
-
-    it 'does not return commit messages from multiline merge commits' do
-      collection = CommitCollection.new(project, multiline_commits).enrich!
-
-      expect(collection.commits).to all( receive(:merge_commit?).and_return(true) )
-      expect(subject).to receive(:commits).and_return(collection)
+    it 'returns the merge request title' do
       expect(subject.default_squash_commit_message).to eq(subject.title)
     end
   end

spec/requests/api/merge_requests_spec.rb

@@ -2533,7 +2533,7 @@ RSpec.describe API::MergeRequests do
       it "results in a default squash commit message when not set" do
         put api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/merge", user), params: { squash: true }
 
-        expect(squash_commit.message).to eq(merge_request.default_squash_commit_message)
+        expect(squash_commit.message.chomp).to eq(merge_request.default_squash_commit_message.chomp)
       end
     end