Re: [PATCH] [RFC] Get subject of current patch in rebase-apply mode

[Daniel Shahaf <d.s@daniel.shahaf.name>]

Daniel Hahler wrote on Sun, Nov 20, 2016 at 02:33:25 +0100:
> From: Daniel Hahler <git@thequod.de>
> 
> ---
>  Functions/VCS_Info/Backends/VCS_INFO_get_data_git | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/Functions/VCS_Info/Backends/VCS_INFO_get_data_git b/Functions/VCS_Info/Backends/VCS_INFO_get_data_git
> index 18ba89a..93172fc 100644
> --- a/Functions/VCS_Info/Backends/VCS_INFO_get_data_git
> +++ b/Functions/VCS_Info/Backends/VCS_INFO_get_data_git
> @@ -236,6 +236,15 @@ elif [[ -d "${gitdir}/rebase-apply" ]]; then
>          done
>          if [[ -f "${patchdir}/msg-clean" ]]; then
>              subject="${$(< "${patchdir}/msg-clean")[(f)1]}"

I use an older version of git that still creates msg-clean files (see
36830), so I rm'd the msg-clean file by hand to test your patch.

> +        else
> +            local maxlines=10
> +            while IFS='\n' read -r;  do

Change '\n' to $'\n'.  (But read the last paragraph first.)

> +                if [[ "$REPLY" == "Subject:"* ]]; then
> +                    subject=${REPLY/(#s)Subject: /}
> +                    break
> +                fi
> +                (( --maxlines )) || break
> +            done < "${patchdir}/$(printf "%04d" $cur)"

I'm not an expert on git internal data structures, but I see two failure
modes to this patch: the file "$patchdir/${(l:4::0:)cur}" might not
exist, or might correspond to a different commit than $cur.  The former
case could be addressed by adding a [[ -f ]] existence check, as
elsewhere in the file.  The latter would cause information for a wrong
commit to be printed instead of a commit hash.  That would be a bug, but
it seems unlikely enough.

So I would suggest two code changes: use «${(l:4::0:)cur}» or the new
'printf -v' instead of a command substitution to save a fork on Cygwin,
and consider adding a [[ -f ]] check to prevent error messages.

One last thing I'd suggest is to consider using VCS_INFO_quilt-patch2subject,
since it implements rfc822 unfolding of long subject lines.

Cheers,

Daniel

>          fi
>          if [[ -f "${patchdir}/original-commit" ]]; then
>              if [[ -n $subject ]]; then
> -- 
> 2.10.2
> 
>