From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 19 Jan 2016 21:46:35 GMT
Subject: Re: git filter-branch not removing commits when it should in 2.7.0
Message-ID: <xmqq37tt9r9g.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20160119213705.GA28656@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

> On Tue, Jan 19, 2016 at 01:35:25PM -0800, Junio C Hamano wrote:
>
>> In other words, would the fix be a one-liner like this?
>> [...]
>> -		tree="$commit^{tree}"
>> +		tree=$(git rev-parse "$commit^{tree}")
>
> Yes, I was just writing up the commit message for it. :-/
>
> It _is_ slower, though, because it introduces an extra rev-parse. When
> we could in fact be getting rid of one. Give me a moment to complete a
> few timing tests and post the results.

Good point.

We should do that rev-parse in the helper function.  That rev-parse
is there only because the skip-empty code wants to know the exact
object name when comparing.  There is no reason for this code to do
it for the helper--the helper, if (and only if) it is called, can
do the rev-parse itself, and we can still omit the overhead when
we are not skipping empty ones.