Re: [RFC 0/9] bisect: allow git bisect to be used with repos containing damaged trees.

From: Jon Seymour <jon.seymour@gmail.com>
Date: Jul 26, 2011, 13:28 UTC
Message-ID: <CAH3AnroGQML+FV_Zh9u35bOBed00bk3qcQ1qA==RpmtTv1zz2w@mail.gmail.com>
In-Reply-To: <m3ei1dsd1x.fsf@localhost.localdomain>

Show 15 quoted lines

> Which means that it works in this case:
>
>
>                        bad bad bad
>                   BAD
>   good good good
>
>
> but won't work in this case:
>
>
>
>   good good good               good good good
>                   bad bad bad
>

Of course, this doesn't mean that bisection is useless, only that you have to choose the right kind of test!

So, while it is true that a commit local test such as those I was proposing (e.g. git ls-tree or even my suggested tweak git rev-list --objects --max-count=1) will be useless unless you happen to start with the tip at the bad commit, it is not true that bisection in general is useless.

For example, Junio's unconstrained git rev-list --objects | git pack-objects test will be sufficient because a history that is

    good good good bad bad bad good good good

according to a commit local test, will be:

     bad bad bad bad bad bad bad good good good

from the point of view of a test that reaches the entire graph reachable from a commit.

It will still be beneficial to do log(N) executions of git rev-list --objects instead of N executions of the same.

jon.