API Endpoint for commit comparison

[delvh]

Feature Description

We now support direct diff comparison for the web (#16635),
but it would be nice to also offer an API endpoint for that.

I think a fitting route for that would be /repos/{owner}/{repo}/git/commits/compare/{baseCommitSHA}/{targetCommitSHA},
or alternatively /repos/{owner}/{repo}/git/commits/compare/{baseCommitSHA}..{targetCommitSHA}.

The return type could be, just as for /repos/{owner}/{repo}/git/commits/{sha}.{diffType} text/plain, with the output of git diff {baseCommitSHA}..{targetCommitSHA}.

Screenshots

No response

[condemil]

I believe it would be beneficial to have not only diff, but also what files were changed. Here is the APIs from other services that have info about files added/modified/deleted/renamed:

https://docs.github.com/en/rest/commits/commits#compare-two-commits
https://docs.gitlab.com/ee/api/repositories.html#compare-branches-tags-or-commits
https://developer.atlassian.com/cloud/bitbucket/rest/api-group-commits/#api-repositories-workspace-repo-slug-diffstat-spec-get