Re: [PATCH 1/2] git-sh-setup: refactor ident-parsing functions

> The only ident-parsing function we currently provide is
> get_author_ident_from_commit. This is not very
> flexible for two reasons:
>
>   1. It takes a commit as an argument, and can't read from
>      commit headers saved on disk.
>
>   2. It will only parse authors, not committers.
>
> This patch provides a more flexible interface which will
> parse multiple idents from a commit provide on stdin. We can
> easily use it as a building block for the current function
> to retain compatibility.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> Since we are counting processes in this series, I should note that this
> actually adds a subshell invocation for each call, since it went from:
>
>   script='...'
>   sed $script
>
> to:
>
>   sed "$(make_script)"
>
> For filter-branch, which is really the only high-performance caller we
> have, this is negated by the fact that it will do author and committer
> at the same time, saving us an extra subshell (in addition to an extra
> sed invocation).

>
>  git-sh-setup.sh | 62 +++++++++++++++++++++++++++++++++++++++------------------
>  1 file changed, 43 insertions(+), 19 deletions(-)
>
> diff --git a/git-sh-setup.sh b/git-sh-setup.sh
> index ee0e0bc..22f0aed 100644
> --- a/git-sh-setup.sh
> +++ b/git-sh-setup.sh
> @@ -191,28 +191,52 @@ get_author_ident_from_commit () {
>  	fi
>  }
>  
> +# Generate a sed script to parse identities from a commit.
> +#
> +# Reads the commit from stdin, which should be in raw format (e.g., from
> +# cat-file or "--pretty=raw").
> +#
> +# The first argument specifies the ident line to parse (e.g., "author"), and
> +# the second specifies the environment variable to put it in (e.g., "AUTHOR"
> +# for "GIT_AUTHOR_*"). Multiple pairs can be given to parse author and
> +# committer.
> +pick_ident_script () {
> +	while test $# -gt 0
> +	do
> +		lid=$1; shift
> +		uid=$1; shift
> +		printf '%s' "
> +		/^$lid /{
> +			s/'/'\\\\''/g
> +			h
> +			s/^$lid "'\([^<]*\) <[^>]*> .*$/\1/'"
> +			s/.*/GIT_${uid}_NAME='&'/p
> +
> +			g
> +			s/^$lid "'[^<]* <\([^>]*\)> .*$/\1/'"
> +			s/.*/GIT_${uid}_EMAIL='&'/p
> +
> +			g
> +			s/^$lid "'[^<]* <[^>]*> \(.*\)$/@\1/'"
> +			s/.*/GIT_${uid}_DATE='&'/p
> +		}
> +		"
> +	done
> +	echo '/^$/q'
> +}
> +
> +# Create a pick-script as above and feed it to sed. Stdout is suitable for
> +# feeding to eval.
> +parse_ident_from_commit () {
> +	LANG=C LC_ALL=C sed -ne "$(pick_ident_script "$@")"
> +}
> +
> +# Parse the author from a commit given as an argument. Stdout is suitable for
> +# feeding to eval to set the usual GIT_* ident variables.
>  get_author_ident_from_commit () {
> -	pick_author_script='
> -	/^author /{
> -		s/'\''/'\''\\'\'\''/g
> -		h
> -		s/^author \([^<]*\) <[^>]*> .*$/\1/
> -		s/.*/GIT_AUTHOR_NAME='\''&'\''/p
> -
> -		g
> -		s/^author [^<]* <\([^>]*\)> .*$/\1/
> -		s/.*/GIT_AUTHOR_EMAIL='\''&'\''/p
> -
> -		g
> -		s/^author [^<]* <[^>]*> \(.*\)$/@\1/
> -		s/.*/GIT_AUTHOR_DATE='\''&'\''/p
> -
> -		q
> -	}
> -	'
>  	encoding=$(git config i18n.commitencoding || echo UTF-8)
>  	git show -s --pretty=raw --encoding="$encoding" "$1" -- |
> -	LANG=C LC_ALL=C sed -ne "$pick_author_script"
> +	parse_ident_from_commit author AUTHOR
>  }
>  
>  # Clear repo-local GIT_* environment variables. Useful when switching to