From: SZEDER Gábor <szeder@ira.uka.de>
Date: Thu, 31 Mar 2011 21:41:18 +0000 (+0200)
Subject: bash prompt: use bash builtins to find out current branch
X-Git-Tag: v1.8.4-rc0~97^2~7
X-Git-Url: https://git.lorimer.id.au/gitweb.git/diff_plain/3a43c4b5bd19528229ef36b28d648d5ac98f15f1?ds=inline;hp=3a43c4b5bd19528229ef36b28d648d5ac98f15f1

bash prompt: use bash builtins to find out current branch

__git_ps1() runs the '$(git symbolic-ref HEAD)' command substitution
to find out whether we are on a branch and to find out the name of
that branch.  This imposes the overhead of fork()ing a subshell and
fork()+exec()ing a git process.

Since HEAD is in most cases a single-line file and the symbolic ref
format is quite simple to recognize and parse, read and parse it using
only bash builtins, thereby sparing all that fork()+exec() overhead.
Don't display the git prompt if reading HEAD fails, because a readable
HEAD is required for a git repository.  HEAD can also be a symlink
symbolic ref (due to 'core.preferSymlinkRefs'), so use bash builtins
for reading HEAD only when HEAD is not a symlink.

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
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