OperationsService: implement UserCommitFiles
This is the generic call for most commit creations initiated by GitLab/Heptapod, except merges.
This includes all editing done through the web (simple file-based interface or WebIDE), the REST API, such as in these examples.
The corresponding method on the Rails side is Gitlab::Mercurial::HgGitRepository#multi_actions
, which overrides Gitlab::Git::Repository
and should be replaced in GitLab::Mercurial::HgitalyRepository
by a bypass of the override.