Add script to verify all merge commits are signed

contrib/verify-commits/verify-commits.sh

@@ -0,0 +1,51 @@
+#!/bin/sh
+
+DIR=$(dirname "$0")
+
+echo "Please verify all commits in the following list are not evil:"
+git log "$DIR"
+
+VERIFIED_ROOT=$(cat "${DIR}/trusted-git-root")
+
+HAVE_FAILED=false
+IS_SIGNED () {
+	if [ $1 = $VERIFIED_ROOT ]; then
+		return 0;
+	fi
+	if ! git -c "gpg.program=${DIR}/gpg.sh" verify-commit $1 > /dev/null 2>&1; then
+		return 1;
+	fi
+	local PARENTS=$(git show -s --format=format:%P $1)
+	for PARENT in $PARENTS; do
+		if IS_SIGNED $PARENT > /dev/null; then
+			return 0;
+		fi
+	done
+	if ! "$HAVE_FAILED"; then
+		echo "No parent of $1 was signed with a trusted key!" > /dev/stderr
+		echo "Parents are:" > /dev/stderr
+		for PARENT in $PARENTS; do
+			git show -s $PARENT > /dev/stderr
+		done
+		HAVE_FAILED=true
+	fi
+	return 1;
+}
+
+if [ x"$1" = "x" ]; then
+	TEST_COMMIT="HEAD"
+else
+	TEST_COMMIT="$1"
+fi
+
+IS_SIGNED "$TEST_COMMIT"
+RES=$?
+if [ "$RES" = 1 ]; then
+	if ! "$HAVE_FAILED"; then
+		echo "$TEST_COMMIT was not signed with a trusted key!"
+	fi
+else
+	echo "There is a valid path from $TEST_COMMIT to $VERIFIED_ROOT where all commits are signed!"
+fi
+
+exit $RES