Re: What's the difference between `git show branch:file | diff -u - file` vs `git diff branch file`?

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 29, 2011, 21:09 UTC
Message-ID: <7v62lf6i2i.fsf@alter.siamese.dyndns.org>
In-Reply-To: <7vty9054qr.fsf@alter.siamese.dyndns.org>

Junio C Hamano <gitster@pobox.com> writes:

Show 22 quoted lines

> Junio C Hamano <gitster@pobox.com> writes:
>
>> Of course the merge machinery does not know anything about pruning with
>> pathspec, so it is understandable (not justifiable) it would walk the full
>> tree.
>>
>> Will try to find time this week to cook up something.
>
> This is still rough, but seems to pass the test suite, and gives me some
> performance boost when applied to the kernel tree:
>
>     (without patch)
>     $ time git diff --raw --cached v2.6.30 -- virt/kvm
>     real    0m0.114s
>     user    0m0.088s
>     sys     0m0.028s
>
>     (with patch)
>     $ time ./git diff --raw --cached v2.6.30 -- virt/kvm
>     real    0m0.075s
>     user    0m0.068s
>     sys     0m0.008s

Heh, this is even better without --cached.

    (without patch)
    $ /usr/bin/time git diff --raw v2.6.27 -- net/ipv6
    real    0m0.538s
    user    0m0.492s
    sys     0m0.048s

    (with patch)
    $ /usr/bin/time git diff --raw v2.6.27 -- net/ipv6
    real    0m0.038s
    user    0m0.028s
    sys     0m0.012s