Re: [PATCH] bash prompt: add option to disable for a repository

From: SZEDER Gábor <szeder@ira.uka.de>
Date: Nov 23, 2013, 16:35 UTC
Message-ID: <20131123163559.GB13824@goldbirke>
In-Reply-To: <1385212703-9611-1-git-send-email-hoxu@users.sf.net>

Hi,

On Sat, Nov 23, 2013 at 03:18:23PM +0200, Heikki Hokkanen wrote:

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> If bash.prompt is set to false, disable the prompt. This is useful
> for huge repositories like the home directory.
> 
> Signed-off-by: Heikki Hokkanen <hoxu@users.sf.net>
> ---
> git-prompt.sh performance seems to be quite bad for big repositories,

Hm, strange. I wonder what can cause performance problems in big repositories.

Sure, there are status indicators that can be expensive, in particular the indicators for dirty index/worktree, untracked files, and divergence from upstream. However, these must be enabled globally by environment variables and even then can already be disabled on a per-repo basis by configuration variables. And the rest of the prompt code should perform pretty much independently from the repository size.

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> so
> without a way to disable it selectively for repositories, it becomes unusable
> for people who have their homedir under git. This patch generalizes the problem
> a bit by allowing the prompt to be disabled by setting bash.prompt to false in
> any repository.
> 
>  contrib/completion/git-prompt.sh | 8 ++++++++
>  1 file changed, 8 insertions(+)

No tests.

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> diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
> index 7b732d2..c982fde 100644
> --- a/contrib/completion/git-prompt.sh
> +++ b/contrib/completion/git-prompt.sh
> @@ -84,6 +84,8 @@
>  # GIT_PS1_SHOWCOLORHINTS to a nonempty value. The colors are based on
>  # the colored output of "git status -sb" and are available only when
>  # using __git_ps1 for PROMPT_COMMAND or precmd.
> +#
> +# To disable prompt for a repository, run "git config bash.prompt false"
>  
>  # check whether printf supports -v
>  __git_printf_supports_v=
> @@ -304,6 +306,12 @@ __git_ps1 ()
>  		return
>  	fi
>  
> +	local prompt_setting
> +	prompt_setting=$(git config --bool bash.prompt)

I spent quite some time eliminating fork()s and exec()s from the prompt, so a fork() for the command substitution's subshell and a fork()+exec() for running a git command in the main code path saddens me deeply ;)

> +	if [ -n "$prompt_setting" ] && [ "$prompt_setting" == "false" ]; then

If $prompt_setting must be false, then checking its non-emptyness is superfluous.

> +		return

You can't just return from __git_ps1(), you must update PS1 in prompt command mode. See the few lines just above this hunk.

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> +	fi
> +
>  	local short_sha
>  	if [ "$rev_parse_exit_code" = "0" ]; then
>  		short_sha="${repo_info##*$'\n'}"
> -- 
> 1.8.4
>