Compare branches across forks

Forking workflows result in branches across multiple forks that frequently need to be compared. This can be done using in a merge request, but there are situations where only a comparison is required.

Comparing branches across forks in the interface and API should be supported.

Previous description

# Compare two different branches from two different repositories using API and UI)

Compare branches from two different repositories using the API and UI.

To enable us to use the API and UI to compare 2 branches from two different repositories.

Proposal

We were trying to compare two different branches from two different repos but this doesn't seem to be possible at the moment. It would be extremely useful for us to do this using the API and also the UI.

Proposal

• Add interface support
• Add API support
  • https://docs.gitlab.com/ce/api/repositories.html#compare-branches-tags-or-commits
  • GET /projects/:id/repository/compare?from=master&to=GROUP/PROJECT:feature

Use cases

For our development team to be able to compare two different branches from two different repositories for code comparison and fault finding.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.

• Feature assurance
• Documentation
• Added to features.yml