Re: [PATCH] rerere-train: modernise a bit

[Johannes Altmanninger <aclopte@gmail.com>]

On Tue, Feb 15, 2022 at 11:05:45PM -0800, Junio C Hamano wrote:
> The script wants to create a list of merges using "rev-list" and
> filters commits that do not have more than one parent, but if we
> always pass "--merges" to "rev-list", there is no need to filter.
> 
> The command uses "git show --pretty=format:..." on a single commit
> while generating progress reports, which means this title line is
> left unterminated.  It should have used --pretty=tformat:...

Yep, tformat is more correct semantically, but it's worth noting that there
is no behavior change here. These commands behave the same

	git show -s --pretty=tformat:"Learning" HEAD
	git show -s --pretty=format:"Learning" HEAD

I guess we automagically add a final newline somewhere, if it's missing.

If there is a final newline ("Learning%n"), then the commands show different
behavior. The subject (%s) can never have a newline, so that's not the
case here.

I'd add something like this (for the lack of knowing where exactly the
implicit newline comes from):

	No harm was done because we implicitly add the trailing newline,
	but it should have used --pretty=tformat:...

> instead, or better yet, use the more modern --format=... to ensure
> that the title line is properly terminated.

> 
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  contrib/rerere-train.sh | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git c/contrib/rerere-train.sh w/contrib/rerere-train.sh
> index 75125d6ae0..499b07e4a6 100755
> --- c/contrib/rerere-train.sh
> +++ w/contrib/rerere-train.sh
> @@ -66,14 +66,9 @@ original_HEAD=$(git rev-parse --verify HEAD) || {
>  
>  mkdir -p "$GIT_DIR/rr-cache" || exit
>  
> -git rev-list --parents "$@" |
> +git rev-list --parents --merges "$@" |
>  while read commit parent1 other_parents
>  do
> -	if test -z "$other_parents"
> -	then
> -		# Skip non-merges
> -		continue
> -	fi
>  	git checkout -q "$parent1^0"
>  	if git merge $other_parents >/dev/null 2>&1
>  	then
> @@ -86,7 +81,7 @@ do
>  	fi
>  	if test -s "$GIT_DIR/MERGE_RR"
>  	then
> -		git show -s --pretty=format:"Learning from %h %s" "$commit"
> +		git show -s --format="Learning from %h %s" "$commit"
>  		git rerere
>  		git checkout -q $commit -- .
>  		git rerere