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

From: Junio C Hamano <[email-masked]>
Date: Sun, 27 Feb 2022 11:07:55 -0800

Johannes Altmanninger <[email-masked]> writes:

> 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

Your observation is not quite right.

The difference between tformat and format does matter in practice,
unless your pager is hiding the difference.

    $ export GIT_PAGER=cat; # disable the pager
    $ git show -s --pretty=format:"%s" HEAD; echo Q
    The eighth batchQ
    $ exit

This episode also exposes another bug in the rerere-train script,
caused by the fact that it lets GIT_PAGER to interfere.

--- >8 ---
Subject: rerere-train: prevent GIT_PAGER from pausing 'git show -s'

The script uses "git show -s --format" 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 for this "git show" invocation to avoid
this.

Signed-off-by: Junio C Hamano <[email-masked]>
---
 contrib/rerere-train.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git c/contrib/rerere-train.sh w/contrib/rerere-train.sh
index 499b07e4a6..2b9df7b6f2 100755
--- c/contrib/rerere-train.sh
+++ w/contrib/rerere-train.sh
@@ -81,7 +81,7 @@ do
 	fi
 	if test -s "$GIT_DIR/MERGE_RR"
 	then
-		git show -s --format="Learning from %h %s" "$commit"
+		git --no-pager show -s --format="Learning from %h %s" "$commit"
 		git rerere
 		git checkout -q $commit -- .
 		git rerere