Adds a test where a branch name is also a valid commit id. Git, the
binary should create an error message which is difficult to parse and
leading to errors later, as seen in: gitlab-org/gitlab-ce#43222

To catch these cases in the future,
gitlab-test@1942eed5cc108b19c7405106e81fa96125d0be22 was created. Which
a branch name matching the commit