[PATCH v2] fixup! mergetool: add automerge configuration

[David Aguilar <davvid@gmail.com>]

"\r\?" in sed is not portable to macOS and possibly others.
"\r" is not valid on Linux with POSIXLY_CORRECT.

Replace "\r" with a substituted variable that contains "\r".
Replace "\?" with "\{0,1\}".

Helped-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: David Aguilar <davvid@gmail.com>
---
This is based on top of fc/mergetool-automerge and can be squashed in
(with the addition of my sign-off) if desired.

Changes since last time:
- printf '\r' instead of printf '\x0d'
- The commit message now mentions POSIXLY_CORRECT.

 git-mergetool.sh | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/git-mergetool.sh b/git-mergetool.sh
index a44afd3822..9029a79431 100755
--- a/git-mergetool.sh
+++ b/git-mergetool.sh
@@ -243,9 +243,16 @@ auto_merge () {
 	git merge-file --diff3 --marker-size=7 -q -p "$LOCAL" "$BASE" "$REMOTE" >"$DIFF3"
 	if test -s "$DIFF3"
 	then
-		sed -e '/^<<<<<<< /,/^||||||| /d' -e '/^=======\r\?$/,/^>>>>>>> /d' "$DIFF3" >"$BASE"
-		sed -e '/^||||||| /,/^>>>>>>> /d' -e '/^<<<<<<< /d' "$DIFF3" >"$LOCAL"
-		sed -e '/^<<<<<<< /,/^=======\r\?$/d' -e '/^>>>>>>> /d' "$DIFF3" >"$REMOTE"
+		cr=$(printf '\r')
+		sed -e '/^<<<<<<< /,/^||||||| /d' \
+			-e "/^=======$cr\{0,1\}$/,/^>>>>>>> /d" \
+			"$DIFF3" >"$BASE"
+		sed -e '/^||||||| /,/^>>>>>>> /d' \
+			-e '/^<<<<<<< /d' \
+			"$DIFF3" >"$LOCAL"
+		sed -e "/^<<<<<<< /,/^=======$cr\{0,1\}$/d" \
+			-e '/^>>>>>>> /d' \
+			"$DIFF3" >"$REMOTE"
 	fi
 	rm -- "$DIFF3"
 }
-- 
2.30.0.rc1.6.g3f22546b2b.dirty