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.

3 files changed, 28 insertions, 22 deletions

diff --git a/app/services/compare_service.rb b/app/services/compare_service.rb
index 5e8fafca98c..4367cb5f615 100644
--- a/app/services/compare_service.rb
+++ b/app/services/compare_service.rb
@@ -3,23 +3,29 @@ require 'securerandom'
 # Compare 2 branches for one repo or between repositories
 # and return Gitlab::Git::Compare object that responds to commits and diffs
 class CompareService
-  def execute(source_project, source_branch, target_project, target_branch, straight: false)
-    source_commit = source_project.commit(source_branch)
-    return unless source_commit
+  attr_reader :source_project, :source_sha
 
-    source_sha = source_commit.sha
+  def initialize(new_source_project, source_branch)
+    @source_project = new_source_project
+    @source_sha = new_source_project.commit(source_branch).try(:sha)
+  end
 
-    # If compare with other project we need to fetch ref first
-    unless target_project == source_project
-      random_string = SecureRandom.hex
+  def execute(target_project, target_branch, straight: false)
+    return unless source_sha
 
-      target_project.repository.fetch_ref(
-        source_project.repository.path_to_repo,
-        "refs/heads/#{source_branch}",
-        "refs/tmp/#{random_string}/head"
-      )
+    # If compare with other project we need to fetch ref first
+    if target_project == source_project
+      compare(target_project, target_branch, straight)
+    else
+      target_project.repository.with_tmp_ref(source_project, source_branch) do
+        compare(target_project, target_branch, straight)
+      end
     end
+  end
+
+  private
 
+  def compare(target_project, target_branch, straight)
     raw_compare = Gitlab::Git::Compare.new(
       target_project.repository.raw_repository,
       target_branch,
diff --git a/app/services/git_operation_service.rb b/app/services/git_operation_service.rb
index 36c8b8ff575..a7d267cd6b4 100644
--- a/app/services/git_operation_service.rb
+++ b/app/services/git_operation_service.rb
@@ -38,15 +38,14 @@ GitOperationService = Struct.new(:user, :repository) do
       branch_name, source_branch_name, source_project)
 
     update_branch_with_hooks(branch_name) do |ref|
-      if repository.project != source_project
-        repository.fetch_ref(
-          source_project.repository.path_to_repo,
-          "#{Gitlab::Git::BRANCH_REF_PREFIX}#{source_branch_name}",
-          "#{Gitlab::Git::BRANCH_REF_PREFIX}#{branch_name}"
-        )
+      if repository.project == source_project
+        yield(ref)
+      else
+        repository.with_tmp_ref(
+          source_project.repository, source_branch_name) do
+            yield(ref)
+          end
       end
-
-      yield(ref)
     end
   end
 
diff --git a/app/services/merge_requests/build_service.rb b/app/services/merge_requests/build_service.rb
index bebfca7537b..a52a94c5ffa 100644
--- a/app/services/merge_requests/build_service.rb
+++ b/app/services/merge_requests/build_service.rb
@@ -16,9 +16,10 @@ module MergeRequests
       messages = validate_branches(merge_request)
       return build_failed(merge_request, messages) unless messages.empty?
 
-      compare = CompareService.new.execute(
+      compare = CompareService.new(
         merge_request.source_project,
-        merge_request.source_branch,
+        merge_request.source_branch
+      ).execute(
         merge_request.target_project,
         merge_request.target_branch,
       )