On 09/05/12 01:44, SZEDER Gábor wrote:
> __git_ps1() prints the branch name, status indicators, etc. to stdout,
> therefore it has to be included in $PS1 through a command substitution
> to display that information in the prompt. The configuration is
> straightforward, but it imposes the overhead of fork()ing a subshell
> for the command substitution.
>
> However, bash has the $PROMPT_COMMAND shell variable, which "if set,
> the value is executed as a command prior to issuing each primary
> prompt" (quoted from bash man page). Its value isn't executed in a
> subshell but in the context of the "main" shell, hence (non-local)
> variables set in invoked shell functions are available when expanding
> $PS1. We can use this facility to avoid that command substitution for
> __git_ps1().
>
> So split out the meat of __git_ps1() into the new
> __git_prompt_command() function, which stores the branch name & co.
> in the $__git_ps1_string variable. This function, as its name
> suggests, should be included in $PROMPT_COMMAND, and $__git_ps1_string
> should in turn be included in $PS1 with a bit of a twist to put the
> parentheses around it:
>
> PROMPT_COMMAND=__git_prompt_command
Rather than overwrite any existing PROMPT_COMMAND, it would be better to
do something like:
PROMPT_COMMAND="__git_prompt_command; $PROMPT_COMMAND"
> PS1='[\u@\h \W${__git_ps1_string:+ ($__git_ps1_string)}]\$ '
>
> Turn __git_ps1() into a wrapper around __git_prompt_command() such
> that it's functionality remains unaltered, so already configured
> prompts won't break.
>
> The whole series speeds up the bash prompt on Windows/MinGW
> immensely, in many cases brings it down to around 10ms on my
> machine while in powersave mode. Here are some timing results in
> three common scenarios (repeated 10 times, because the after cases
> were too fast to measure a single execution accurately with 'time'):
>
> In my home directory, i.e. not in a git repository, before:
>
> /c/Users/szeder
> $ time for i in {0..9} ; do prompt=$(__git_ps1) ; done
>
> real 0m0.952s
> user 0m0.214s
> sys 0m0.444s
>
> After:
>
> /c/Users/szeder
> $ time for i in {0..9} ; do __git_prompt_command ;
> prompt=${__git_ps1_string:+ ($__git_ps1_string)} ; done
>
> real 0m0.718s
> user 0m0.136s
> sys 0m0.354s
>
> After, with discovery across filesystems enabled:
>
> /c/Users/szeder
> $ time for i in {0..9} ; do __git_prompt_command ;
> prompt=${__git_ps1_string:+ ($__git_ps1_string)} ; done
>
> real 0m0.078s
> user 0m0.016s
> sys 0m0.062s
>
> At the top of a work tree, before:
>
> /c/Users/szeder/repo (master)
> $ time for i in {0..9} ; do prompt=$(__git_ps1) ; done
>
> real 0m2.901s
> user 0m0.391s
> sys 0m1.468s
>
> After:
>
> /c/Users/szeder/repo (master)
> $ time for i in {0..9} ; do __git_prompt_command ;
> prompt=${__git_ps1_string:+ ($__git_ps1_string)} ; done
>
> real 0m0.094s
> user 0m0.047s
> sys 0m0.047s
>
> In a subdirectory, stash indicator enabled, before:
>
> /c/Users/szeder/repo/subdir (master $)
> $ time for i in {0..9} ; do prompt=$(__git_ps1) ; done
>
> real 0m4.118s
> user 0m0.468s
> sys 0m2.056s
>
> After:
>
> /c/Users/szeder/repo/subdir (master $)
> $ time for i in {0..9} ; do __git_prompt_command ;
> prompt=${__git_ps1_string:+ ($__git_ps1_string)} ; done
>
> real 0m0.858s
> user 0m0.152s
> sys 0m0.322s
>
> After, discovery across filesystems enabled:
>
> /c/Users/szeder/repo/subdir (master $)
> $ time for i in {0..9} ; do __git_prompt_command ;
> prompt=${__git_ps1_string:+ ($__git_ps1_string)} ; done
>
> real 0m0.109s
> user 0m0.047s
> sys 0m0.063s
>
> Well, that's about 97% improvement.
>
> The performance gain on Linux is smaller, the latter case goes down
> from 0.264s to 0.047, but since it was fast enough to begin with I
> won't lengthen this commit message with further timing results on
> Linux.
>
> Signed-off-by: SZEDER Gábor <szeder@xxxxxxxxxx>
> ---
>
> We had some discussions recently about putting user-facing functions into
> a separate "namespace". This patch doesn't take that into account, but
> once a consensus is reached __git_prompt_command() should be put in that
> namespace.
>
> contrib/completion/git-completion.bash | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
> index 5ea19018..1c29f3d0 100755
> --- a/contrib/completion/git-completion.bash
> +++ b/contrib/completion/git-completion.bash
> @@ -29,6 +29,11 @@
> # are currently in a git repository. The %s token will be
> # the name of the current branch.
> #
> +# Alternatively, to make the above Bash prompt a bit faster:
> +# PROMPT_COMMAND=__git_prompt_command
As above, I'd recommend a simple documentation change:
PROMPT_COMMAND="__git_prompt_command; $PROMPT_COMMAND"
(to show people how to chain any other prompt commands they have)
> +# PS1='[\u@\h \W${__git_ps1_string:+ ($__git_ps1_string)}]\$ '
> +# GIT_DISCOVERY_ACROSS_FILESYSTEM=true
> +#
> # In addition, if you set GIT_PS1_SHOWDIRTYSTATE to a nonempty
> # value, unstaged (*) and staged (+) changes will be shown next
> # to the branch name. You can configure this per-repository
> @@ -258,11 +263,12 @@ __git_ps1_show_upstream ()
> }
>
>
> -# __git_ps1 accepts 0 or 1 arguments (i.e., format string)
> -# returns text to add to bash PS1 prompt (includes branch name)
> -__git_ps1 ()
> +# Stores the text to be added to the bash prompt (branch name, status
> +# indicators, etc.) in the $__git_ps1_string variable.
> +__git_prompt_command ()
> {
> local __git_dir=""
> + __git_ps1_string=""
> __gitdir >/dev/null
> if [ -z "$__git_dir" ]; then
> return
> @@ -365,7 +371,18 @@ __git_ps1 ()
> fi
>
> local f="$w$i$s$u"
> - printf -- "${1:- (%s)}" "$c${b##refs/heads/}${f:+ $f}$r$p"
> + __git_ps1_string="$c${b##refs/heads/}${f:+ $f}$r$p"
> +}
> +
> +# __git_ps1 accepts 0 or 1 arguments (i.e., format string)
> +# returns text to add to bash PS1 prompt (includes branch name)
> +__git_ps1 ()
> +{
> + local __git_ps1_string
> + __git_prompt_command
> + if [ -n "$__git_ps1_string" ]; then
> + printf -- "${1:- (%s)}" "$__git_ps1_string"
> + fi
How hard/appropriate would it be to export individual parts of the
prompt here? Something like:
__git_ps1_string_dirtystate="$i"
__git_ps1_string_untrackedfiles="$u"
There have been requests in the past to let people individually
colourise different bits of the prompt, which this would make practical.
> }
>
> __gitcomp_1 ()
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