Subject: Re: [PATCH] completion: fix issue with process substitution not working on Git for Windows

From: Johannes Sixt <[email-masked]>
Date: Tue, 25 Oct 2011 22:39:40 +0200

Am 25.10.2011 20:01, schrieb Stefan Naewe:
> Git for Windows comes with a bash that doesn't support process substitution.
> It issues the following error when using git-completion.bash with
> GIT_PS1_SHOWUPSTREAM set:
> 
> $ export GIT_PS1_SHOWUPSTREAM=1
> sh.exe": cannot make pipe for process substitution: Function not implemented
> sh.exe": cannot make pipe for process substitution: Function not implemented
> sh.exe": <(git config -z --get-regexp '^(svn-remote\..*\.url|bash\.showupstream)$' 2>/dev/null | tr '\0\n' '\n '): ambiguous redirect
> 
> Replace the process substitution with a simple "echo $var | while...".
> 
> Signed-off-by: Stefan Naewe <[email-masked]>
> ---
>  contrib/completion/git-completion.bash |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
> index 8648a36..926db80 100755
> --- a/contrib/completion/git-completion.bash
> +++ b/contrib/completion/git-completion.bash
> @@ -110,6 +110,8 @@ __git_ps1_show_upstream ()
>  	local upstream=git legacy="" verbose=""
>  
>  	# get some config options from git-config
> +	output="$(git config -z --get-regexp '^(svn-remote\..*\.url|bash\.showupstream)$' 2>/dev/null | tr '\0\n' '\n ')"
> +	echo "$output" | \
>  	while read key value; do
>  		case "$key" in
>  		bash.showupstream)
> @@ -125,7 +127,7 @@ __git_ps1_show_upstream ()
>  			upstream=svn+git # default upstream is SVN if available, else git
>  			;;
>  		esac
> -	done < <(git config -z --get-regexp '^(svn-remote\..*\.url|bash\.showupstream)$' 2>/dev/null | tr '\0\n' '\n ')
> +	done
>  
>  	# parse configuration values
>  	for option in ${GIT_PS1_SHOWUPSTREAM}; do

Are you sure that the result still works as intended? The while loop
sets a few variables. When you place it in a pipe, the loop runs in a
subshell, and subsequent code will not see the modified values. Unless
bash knows how to optimize away the subshell, that is.

OTOH, when you use while ...; do ...; done < <(...), the while loop is
not in a subshell.

An alternative is to use:  while ...; do ...; done <<< "$output"

BTW, you don't need to protect the end-of-line with a backslash if the
line ends with the pipe symbol.

-- Hannes