Improvement: Revert commit funcionality

[arvist]

Could not find revert functionality in CommitsAPI sub API
It has been recently added in GitLab API:
https://docs.gitlab.com/ee/api/commits.html#revert-a-commit

[gmessner]

@arvist
The CommitsApi.revertCommit() method has been added and released in version 4.10.19.

If you could verify and close this issue I would appreciate it.

[arvist]

@gmessner Tested revert functionality - works great.
Thanks, for quick turnaround