test look for upstream master by default, and minor fixes

This changes the test to look for the upstream master in the user current config and use that as the test reference by default. This seems like a more sensible default in general, and it's easy enough to fall back to HEAD if need be ('-g HEAD').

This also fixes some things from the last commit:

• fixes the MR CI pipeline
• adds better command line documentation to the test
• fixes command help
• fixes bug in test cache pruing

@christopher.wipf @evan.hall @kevin.kuns I'm really sorry guys, I was finally convinced by your arguments in the end and made this patch that I was going to amend to the other, apparently while it was being merged. I realized it's not so hard to try to resole the upstream master, and also pretty easy enough to compare against HEAD with -g HEAD. So I say we go with this.

This also fixes some bugs in the previous commit that I didn't catch until I did the work on this.

approved this merge request

Looks good to me, I'll go ahead and merge.

merged

mentioned in commit 85c771da

thanks @christopher.wipf