1 files changed, 18 insertions, 1 deletions
diff --git a/app/services/compare_service.rb b/app/services/compare_service.rb
index 48ad7fab4e6..4c8b35edff8 100644
--- a/app/services/compare_service.rb
+++ b/app/services/compare_service.rb
@@ -1,3 +1,5 @@
+require 'securerandom'
+
 # Compare 2 branches for one repo or between repositories
 # and return Gitlab::CompareResult object that responds to commits and diffs
 class CompareService
@@ -12,7 +14,22 @@ class CompareService
         )
       )
     else
-      raise 'Implement me'
+      random_string = SecureRandom.hex
+      target_project.repository.fetch_ref(
+        source_project.repository.path_to_repo,
+        "refs/heads/#{source_branch}",
+        "refs/tmp/#{random_string}/head"
+      )
+
+      source_sha = source_project.commit(source_branch).sha
+
+      Gitlab::CompareResult.new(
+        Gitlab::Git::Compare.new(
+          target_project.repository.raw_repository,
+          target_branch,
+          source_sha,
+        )
+      )
     end
   end
 end