Allow retrieving commits for merge request

[rollie42]

Description of the problem, including code/CLI snippet

API does not support getting commits for merge request (or documentation hasn't been updated)

see: https://docs.gitlab.com/ce/api/merge_requests.html#get-single-mr-commits

Expected Behavior

project.commits() should return a list of commits

Actual Behavior

Not defined in docs

Specifications

v4 (and v3?)

[gpocentek]

Hi @rollie42

This is implemented, you can use the commits() method on ProjectMergeRequest objects: https://github.com/python-gitlab/python-gitlab/blob/master/gitlab/v4/objects.py#L1561-L1587

This is documented in the v4 API: http://python-gitlab.readthedocs.io/en/stable/api/gitlab.v4.html#gitlab.v4.objects.ProjectMergeRequest.commits but I'll add an example.