Re: [PATCH v2] rerere-train: two fixes to the use of "git show -s"

[Johannes Altmanninger <aclopte@gmail.com>]

On Sun, Feb 27, 2022 at 02:09:24PM -0800, Junio C Hamano wrote:
> The script uses "git show -s" to display the title of the merge
> commit being studied, without explicitly disabling the pager, which
> is not a safe thing to do in a script.
> 
> For example, when the pager is set to "less" with "-SF" options (-S
> tells the pager not to fold lines but allow horizontal scrolling to
> show the overly long lines, -F tells the pager not to wait if the
> output in its entirety is shown on a single page), and the title of
> the merge commit is longer than the width of the terminal, the pager
> will wait until the end-user tells it to quit after showing the
> single line.
> 
> Explicitly disable the pager with this "git show" invocation to fix
> this.
> 
> The command uses the "--pretty=format:..." format, which adds LF in
> between each pair of commits it outputs, which means that the label
> for the merge being learned from will be followed by the next
> message on the same line.  "--pretty=tformat:..." is what we should
> instead, which adds LF after each commit, or a more modern way to
> spell it, i.e. "--format=...".  This existing breakage becomes
> easier to see, now we no longer use the pager.

Sounds good (definitely better than two separate commits).

> 
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
> 
>  * Relative to the initial version, the "--no-merges" change has

it was "--merges", not "--no-merges"

>    been removed because the end user can still give --merges from
>    the command line and the filtering of merges done by the script
>    is still needed for correctness.

You probably mean that the user can pass "--no-merges HEAD"
but that would just make the effective command

	git rev-list --merges --no-merges HEAD

which outputs nothing. I don't think `git rev-list --merges "$@"` will
ever output non-merge commits, so the filtering should not be necessary.

> 
>  contrib/rerere-train.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/contrib/rerere-train.sh b/contrib/rerere-train.sh
> index 75125d6ae0..26b724c8c6 100755
> --- a/contrib/rerere-train.sh
> +++ b/contrib/rerere-train.sh
> @@ -86,7 +86,7 @@ do
>  	fi
>  	if test -s "$GIT_DIR/MERGE_RR"
>  	then
> -		git show -s --pretty=format:"Learning from %h %s" "$commit"
> +		git --no-pager show -s --format="Learning from %h %s" "$commit"
>  		git rerere
>  		git checkout -q $commit -- .
>  		git rerere
> -- 
> 2.35.1-354-g715d08a9e5
>