API support for the 'since' and 'until' operators on commit requests
What does this MR do?
This merge request addresses issue gitlab-org/gitlab-ce#15001 where the since and until parameters needs to be added to the commits API endpoint.
Are there points in the code the reviewer needs to double check?
Params parsing for the since/until parameters. I just added a specific parser for what kind of stringified dates we expect. I cannot see any other example on the code base, but I would suggest to probably use the support built-in on the Grape gem. As that will be a more complex feature request I just go to the easier path a implement one simple method for this use case.
Probably you will notice that the issue define since and until and that we only use those string to get the parameters and later we use after and before that's why until is a reserved word so I decided to use always after and before than are equivalent.
Why was this MR needed?
To support new options on the commits API endpoint of the gitlab-ce apps.