Re: [RFC/PATCH]: reverse bisect v 2.0

[Jeff King <peff@peff.net>]

On Tue, Oct 11, 2011 at 09:57:13PM -0700, Junio C Hamano wrote:

> With an obvious addition of non-interactive short-cut subcommands "git
> bisect yes" and "git bisect no", I think --removed= is a much better
> wording than --used-to= I suggested in the discussion.

Agreed.

> I however am still worried about the flipping of the mapping between
> <good,bad> and <yes,no> this design requires. What are we going to do to
> the labels of low-level machinery (i.e $GIT_DIR/refs/bisect/bad and
> $GIT/refs/bisect/good)? They appear in "bisect visualize" and I was hoping
> that it would be simpler in the code if we do not have to change them in
> such a way that depends on this introduced/removed switch, and that was
> the reason why I was trying to see if we can solve this without the
> switchable mapping between <good,bad> and <yes,no>.

Hmm. I hadn't thought about the labels. In a yes/no situation, though,
couldn't you use the labels as the user sees them?

Then it is simply a matter of flipping yes/no inside the bisect script
whenever we interact with the user (i.e., "git bisect yes") or when we
interact with the on-disk labels.

Certainly it's more complex than not allowing reversing, though.

> More specifically, I was hoping that we can rename "good" to "old" and
> "bad" to "new" unconditionally and be done with it. We would ask the user
> "What did the code used to do in the olden days?" and "Does this version
> behave the same as it used to?". The possible answers the user can give
> are "git bisect old" (it behaves the same as the older versions) and "git
> bisect new" (it behaves the same as the newer versions). Then we do not
> have to worry about having to flip the meaning of <yes> and <no> at the UI
> level.

Hmm. I think this is not quite as nice, but it is way simpler. It may be
worth trying for a bit to see how people like it. If they don't, the
cost of failure is that we have to maintain "old/new" forever, even
after we implement a yes/no reversible scheme. But maintaining the
old/new mapping from yes/no would not be any harder than the good/bad
mapping, which we would need to do anyway.

So it sounds like a reasonable first step.

-Peff