Add check to git-test for branch origin.

It will now exit if the branch has been started from develop
or has had develop merged in.
Refs #6964
Make 'git test fail' more tolerant of bad merges/rebases.

If a 'test start' merge fails then fail can now just reset
without having to run 'git merge --abort'.
Refs #6964
Merge remote-tracking branch 'origin/feature/6964_git_test_macro_check_develop'