Fix merge request 500 when first commit does not have a parent
Fixes gitlab-org/gitlab-ce#19384
Under some strange circumstances, a merge request may contain a first commit that has no parent. In this case the merge request widget may fail when trying to find the source_sha_parent
. This merge request adds a simple check to see if there are any parents before calling first.sha
on the commit.
Things to check
I didn't write any tests for this. I'm not 100% sure of the best way to create a commit in the merge request that has no parents.
@dbalexandre Do you mind doing a review, please? Maybe you have some ideas on writing a test?