tests: Add a test for pull+deploy of specific "bare" commit

[cgwalters]

This is the "pull an older version" that's now supported since
36d65b3

However...this test does not fail when I revert the commits that were supposed to make it work. I'm still debugging that.

[cgwalters]

And now that I had a chance to test on top of #146 - this test correctly fails with the f4d832475edcb2bf6fdae2eaa8f8cb1b6a02abf0 commit reverted locally.

[cgwalters]

To clarify, what was confusing is that the "no prune" behavior also occurred when transitioning from 0 > 1 deployments, as well as 1 -> 0. In the normal case of a running system you have at least 1, but my test only had 0.

[cgwalters]

@mbarnes ^

[mbarnes]

Looks good, and I gotta remember to use rev-parse in future tests. That's handy.

I think it wouldn't hurt to link to this PR in the test script for posterity. Sometimes it's not entirely clear what a test is testing for.

Otherwise, 👍

[cgwalters]

Not having a link to the PR conversation is a major gap in this workflow now. =(

Maybe we can just do it manually - submit your PR, then use git rebase to add the PR link to the bottom of each commit? Could be automated.

[cgwalters]

Thanks though, pushed as b6e2eaf