Fix order of branches in git diff when preparing sparse checkout rebase

3 files changed, 42 insertions, 1 deletions

diff --git a/changelogs/unreleased/wc-rebase-diff-reorder.yml b/changelogs/unreleased/wc-rebase-diff-reorder.yml
new file mode 100644
index 000000000..da6fbdd31
--- /dev/null
+++ b/changelogs/unreleased/wc-rebase-diff-reorder.yml
@@ -0,0 +1,5 @@
+---
+title: Fix order of branches in git diff when preparing sparse checkout rebase
+merge_request: 1716
+author:
+type: other
diff --git a/ruby/lib/gitlab/git/repository.rb b/ruby/lib/gitlab/git/repository.rb
index 73feb2e74..c3d3ab3a2 100644
--- a/ruby/lib/gitlab/git/repository.rb
+++ b/ruby/lib/gitlab/git/repository.rb
@@ -358,7 +358,7 @@ module Gitlab
           remote_repo_path = remote_repository.path
         end
 
-        diff_range = "#{branch}...#{remote_branch}"
+        diff_range = "#{remote_branch}...#{branch}"
         diff_files = begin
                        run_git!(
                          %W[diff --name-only #{diff_range}]
diff --git a/ruby/spec/lib/gitlab/git/repository_spec.rb b/ruby/spec/lib/gitlab/git/repository_spec.rb
index 1b5828877..417f60501 100644
--- a/ruby/spec/lib/gitlab/git/repository_spec.rb
+++ b/ruby/spec/lib/gitlab/git/repository_spec.rb
@@ -608,6 +608,42 @@ describe Gitlab::Git::Repository do # rubocop:disable Metrics/BlockLength
     end
   end
 
+  describe '#rebase' do
+    let(:repository) { mutable_repository }
+    let(:rebase_id) { '2' }
+    let(:branch_name) { 'rd-add-file-larger-than-1-mb' }
+    let(:branch_sha) { 'c54ad072fabee9f7bf9b2c6c67089db97ebfbecd' }
+    let(:remote_branch) { 'master' }
+
+    subject do
+      opts = {
+        branch: branch_name,
+        branch_sha: branch_sha,
+        remote_repository: repository,
+        remote_branch: remote_branch
+      }
+
+      repository.rebase(user, rebase_id, opts)
+    end
+
+    describe 'sparse checkout' do
+      let(:expected_files) { %w[files/images/emoji.png] }
+
+      it 'lists files modified in source branch in sparse-checkout' do
+        allow(repository).to receive(:with_worktree).and_wrap_original do |m, *args|
+          m.call(*args) do
+            sparse = repository.path + "/worktrees/rebase-#{rebase_id}/info/sparse-checkout"
+            diff_files = IO.readlines(sparse, chomp: true)
+
+            expect(diff_files).to eq(expected_files)
+          end
+        end
+
+        subject
+      end
+    end
+  end
+
   describe '#squash' do
     let(:repository) { mutable_repository }
     let(:squash_id) { '1' }