Re: AAARGH bisection is hard (Re: [2.6.39 regression] X locks up hard right after logging in)

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: May 13, 2011, 18:41 UTC
Message-ID: <BANLkTi=smoaARKyzWxFjid-E7qehmyAX8w@mail.gmail.com>
In-Reply-To: <4DCD79A0.7000500@kdbg.org>

On Fri, May 13, 2011 at 11:34 AM, Johannes Sixt <j6t@kdbg.org> wrote:

Show 16 quoted lines

> Am 13.05.2011 19:54, schrieb Linus Torvalds:
>> For example, in your case, since you had certain requirements of
>> support that simply didn't exist earlier, something like
>>
>>    git bisect requires v2.6.38
>>
>> would have been really useful - telling git bisect that any commit
>> that cannot reach that required commit is not even worth testing.
>
> You can already have this with
>
>   git bisect good v2.6.38
>
> It sounds a bit unintuitive, but with a slight mind-twist it can even be
> regarded as correct in a mathematical sense: when the precondition is
> false, the result is true. ;-)

No. That's not the same thing AT ALL.

When you say that v2.6.38 is good, that means that everything that can be reached from 2.6.38 is good.

NOT AT ALL the same thing as "git bisect requires v2.6.38" would be.

The "requires v2.6.38" would basically say that anything that doesn't contain v2.6.38 is "off-limits". It's fine to call them "good", but that's not the same thing as "git bisect good v2.6.38".

Why?

Think about it. It's the "reachable from v2.6.38" vs "cannot reach v2.6.38" difference. That's a HUGE difference.

                       Linus