Support platformCommit on the GitLab platform

[gauravluckme]

Feature Request

This feature request is specifically about extending the existing platformCommit implementation for Gitlab, so Renovate can create commits using API.

Proposed change(s)

platformCommit currently only works on GitHub, where Renovate uses the createCommitOnBranch GraphQL mutation to create commits via the API instead of local git operations. Requesting the same for GitLab.
GitLab's REST API already has the equivalent capability via the Commits API (POST /projects/:id/repository/commits), which accepts a branch, commit message, and an actions array supporting create/update/delete/move on multiple files in one commit — functionally the same shape Renovate already builds for GitHub's API commits.

Why this is useful:

• Enables platformCommit workflows for GitLab users who want API-native commits.
• Verified signed commits for compliance/security.
• Keeps existing behavior for auto/disabled paths while adding explicit enabled support.

[jamietanna]

Does the use of the GitLab API to author a commit result in a signed commit? That doesn't seem to be the case by default (looking at a project of mine that uses the API to create commits)

But yes, this generally is a reasonable idea

Keeps existing behavior for auto/disabled paths while adding explicit enabled support.

What do you mean by this?

[gauravluckme]

Does the use of the GitLab API to author a commit result in a signed commit?

No, however with Reject unsigned commits enabled in the Gitlab push rules, GitLab still allows commits created by GitLab itself (UI and API paths).

Keeps existing behavior for auto/disabled paths while adding explicit enabled support.

This basically means how platformCommit is structured today and how a GitLab feature should slot into it without disrupting what already works. And it will only work for Gitlab when it is enabled.

[gauravluckme]

Can you please let me know if I can go ahead with the PR for this feature request?

[jamietanna]

Yes I think that makes sense - cc @RahulGautamSingh as you may want to do some testing for this :)

[jamietanna]

Raised #44225 to cover this