Introduce Repository#with_tmp_ref which we need

commits from the other repository. We'll cleanup
the tmp ref after we're done with our business.

2 files changed, 17 insertions, 1 deletions

diff --git a/app/models/merge_request_diff.rb b/app/models/merge_request_diff.rb
index b8f36a2c958..7946d8e123e 100644
--- a/app/models/merge_request_diff.rb
+++ b/app/models/merge_request_diff.rb
@@ -169,7 +169,8 @@ class MergeRequestDiff < ActiveRecord::Base
     # When compare merge request versions we want diff A..B instead of A...B
     # so we handle cases when user does squash and rebase of the commits between versions.
     # For this reason we set straight to true by default.
-    CompareService.new.execute(project, head_commit_sha, project, sha, straight: straight)
+    CompareService.new(project, head_commit_sha).
+      execute(project, sha, straight: straight)
   end
 
   def commits_count
diff --git a/app/models/repository.rb b/app/models/repository.rb
index 73a9e269a65..ced68b9d274 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -1099,6 +1099,21 @@ class Repository
     Gitlab::Popen.popen(args, path_to_repo).first.lines.map(&:strip)
   end
 
+  def with_tmp_ref(source_repository, source_branch_name)
+    random_string = SecureRandom.hex
+
+    fetch_ref(
+      source_repository.path_to_repo,
+      "#{Gitlab::Git::BRANCH_REF_PREFIX}#{source_branch_name}",
+      "refs/tmp/#{random_string}/head"
+    )
+
+    yield
+
+  ensure
+    FileUtils.rm_rf("#{path_to_repo}/refs/tmp/#{random_string}")
+  end
+
   def fetch_ref(source_path, source_ref, target_ref)
     args = %W(#{Gitlab.config.git.bin_path} fetch --no-tags -f #{source_path} #{source_ref}:#{target_ref})
     Gitlab::Popen.popen(args, path_to_repo)