Only way to mark a revision as fixing another bad revision is 'rollback=xxxx'

[Данило Шеган]

This is something that commonly happens in development: we find a problem with a revision, and land a fix for it. I've noticed it with a fix for bug 118284, where original fix landed in 12102, was found to be broken and couldn't be rolled out (thus marked as bad-commit-12102), and later a problem in the fix was fixed in 12121 (and marked as qa-ok).

At the moment, it's impossible to indicate this data to the qa-tagger, so we'll have to wait for all revisions up to 12121 to "clear" before removing the bad-commit tag. Yet, that commit is still bad, and it'd be good to keep that information around.

For tagger to know about this properly today, we should have first landed a rollback of 12102, and then landed a full fix. That's sometimes more effort than just fixing something.

[Robert Collins (lifeless)]

You can mark the fix with rollback=1234 but that does feel unpleasant ;)