From ccbb5aad8aec65073894715bf8bfdd247654491b Mon Sep 17 00:00:00 2001
From: Junio C Hamano <gitster@pobox.com>
Date: Sat, 18 Jul 2026 19:23:57 -0700
Subject: [PATCH] Meta/basecheck: validate the synthetic base of topics

---
 basecheck.sh | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100755 basecheck.sh

diff --git a/basecheck.sh b/basecheck.sh
new file mode 100755
index 0000000000..6ca58bc963
--- /dev/null
+++ b/basecheck.sh
@@ -0,0 +1,51 @@
+#!/bin/sh
+
+if test $# = 3
+then
+	merge=$1 base=$2 target=$3
+	label=$(git log --oneline -1 "$merge")
+
+	base0=$(git rev-parse "$base^0") &&
+	base1=$(git rev-parse "$merge^2") &&
+	test "$base0" = "$base1" || {
+		echo >&2 "BAD: stale $base in $target"
+		exit 2
+	}
+
+	cd ../git.one || exit 1
+	if grep "$merge" :basecheck-tested-ok >/dev/null
+	then
+		exit 0
+	elif grep "$merge" :basecheck-tested-ng >/dev/null
+	then
+		echo >&2 "BAD (again): $label"
+		exit 1
+	fi
+
+	echo >&2 "Testing $merge $target"
+	git reset --quiet --hard "$merge" || exit 1
+	if Meta/Make -s -j32 >:basecheck-errors 2>&1
+	then
+		echo >&2 "OK: $label"
+		echo "$merge" >>:basecheck-tested-ok
+		exit 0
+	else
+		echo "$merge" >>:basecheck-tested-ng
+		cat ":basecheck-errors"
+		echo >&2 "BAD: $label"
+		exit 1
+	fi
+
+	exit 0 ;# just in case
+fi
+
+git log --oneline --abbrev=-1 --min-parents=2 ..seen |
+sed -n -e "s|^\([0-9a-f]*\) Merge branch '\(.*\)' into \(../..*\)$|\1 \2 \3|p" |
+{
+	exit=
+	while read merge base target
+	do
+		"$0" "$merge" "$base" "$target" </dev/null || exit=$?
+	done
+	exit $exit
+}
-- 
2.47.3