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From: SZEDER =?iso-8859-1?Q?G=E1bor?= <szeder@ira.uka.de>
Subject: Re: [PATCH 2/2] completion: split __git_ps1 into a separate script
Date: Fri, 25 May 2012 09:35:06 +0200
Message-ID: <20120525073506.GD2052@goldbirke>
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Cc: Felipe Contreras <felipe.contreras@gmail.com>,
	Ville =?iso-8859-1?Q?Skytt=E4?= <ville.skytta@iki.fi>,
	Thomas Rast <trast@student.ethz.ch>,
	Kerrick Staley <mail@kerrickstaley.com>,
	Dan McGee <dan@archlinux.org>,
	Zbigniew =?utf-8?Q?J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>,
	git@vger.kernel.org, Marius Storm-Olsen <mstormo@gmail.com>,
	Junio C Hamano <gitster@pobox.com>
To: Ted Pavlic <ted@tedpavlic.com>
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On Thu, May 24, 2012 at 11:36:45PM -0400, Ted Pavlic wrote:
> > You mean a real git command, which does the same as __gitdir()?  I
> > don't like that, because it will always require 2 fork()s and an
> > exec() and would be slow on Windows.
>=20
> Interesting. I guess I didn't realize bash completion was an issue fo=
r most
> Windows users. Is it?

It is.  Emulating fork() and exec() is very expensive, so every
subshell, external command, or especially git command in a command
substitution costs dearly.  And the completion script uses many git
commands and even more subshells.

Case in point is __git_ps1() and __gitdir().  There are scenarios
where displaying the git-specific bash prompt takes more than 400ms on
Windows, while displaying the same prompt takes only about 26ms on
Linux on the same hardware.

  http://thread.gmane.org/gmane.comp.version-control.git/197432


Best,
G=E1bor