Display `parent_ids` in merge request commits API response

Vasilii Iakliushinrequested to merge
496665-preload-commits-from-gitaly into master

What does this MR do and why?

Contributes to #496665 (closed)

Problem

Merge request commits are stored in the database without information about their parent_ids. As a result, commits created from DB records are missing this data.

Solution

Load commit content from Gitaly to have access to full commit information.

References

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MR acceptance checklist

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Screenshots or screen recordings

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Before After
Screenshot_2025-02-14_at_15.08.43 Screenshot_2025-02-14_at_15.08.58

How to set up and validate locally

  1. Enable feature flag

    Feature.enable(:commits_from_gitaly)

  2. Visit merge request commits API endpoint (http://gdk.test:3000/api/v4/projects/462/merge_requests/1/commits)

  3. parent_ids value should be defined for commits (when FF is disabled, it will be missing)

  4. Find a merge request diff version from this endpoint (http://gdk.test:3000/api/v4/projects/462/merge_requests/1/versions/)

  5. Visit merge request diff version page (http://gdk.test:3000/api/v4/projects/462/merge_requests/1/versions/2180)

  6. parent_ids value should be defined for commits (when FF is disabled, it will be missing. Note endpoint response is cached)

Related to #496665 (closed)

Merge request reports