Comment API improvement

Created by: zlx

Hi, Guys

I'm work on a project to automatically review code syntax, like hound did, but for gitlab project. now I have meet some problems:

_I want to add some comments on special line in a MR.!!_ And I find an API POST /projects/:id/merge_request/:merge_request_id/comments, but it do not support assign line and line_path.

Thanks Jeroen Jacobs, with the patch https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/137, I can add some commets with line and line_path to special commit.

but things seems more complex than that, if I use the new API(comment on special commit), I need to know which commit does the change file belongs to, I can not find any API can provide this.

maybe I'm missing somethings. Can anybody help me?