test "commit -S" and "log --show-signature"

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7510-signed-commit.sh

@@ -0,0 +1,71 @@
+#!/bin/sh
+
+test_description='signed commit tests'
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-gpg.sh"
+
+test_expect_success GPG 'create signed commits' '
+	echo 1 >file && git add file &&
+	test_tick && git commit -S -m initial &&
+	git tag initial &&
+	git branch side &&
+
+	echo 2 >file && test_tick && git commit -a -S -m second &&
+	git tag second &&
+
+	git checkout side &&
+	echo 3 >elif && git add elif &&
+	test_tick && git commit -m "third on side" &&
+
+	git checkout master &&
+	test_tick && git merge -S side &&
+	git tag merge &&
+
+	echo 4 >file && test_tick && git commit -a -m "fourth unsigned" &&
+	git tag fourth-unsigned &&
+
+	test_tick && git commit --amend -S -m "fourth signed"
+'
+
+test_expect_success GPG 'show signatures' '
+	(
+		for commit in initial second merge master
+		do
+			git show --pretty=short --show-signature $commit >actual &&
+			grep "Good signature from" actual || exit 1
+			! grep "BAD signature from" actual || exit 1
+			echo $commit OK
+		done
+	) &&
+	(
+		for commit in merge^2 fourth-unsigned
+		do
+			git show --pretty=short --show-signature $commit >actual &&
+			grep "Good signature from" actual && exit 1
+			! grep "BAD signature from" actual || exit 1
+			echo $commit OK
+		done
+	)
+'
+
+test_expect_success GPG 'detect fudged signature' '
+	git cat-file commit master >raw &&
+
+	sed -e "s/fourth signed/4th forged/" raw >forged1 &&
+	git hash-object -w -t commit forged1 >forged1.commit &&
+	git show --pretty=short --show-signature $(cat forged1.commit) >actual1 &&
+	grep "BAD signature from" actual1 &&
+	! grep "Good signature from" actual1
+'
+
+test_expect_success GPG 'detect fudged signature with NUL' '
+	git cat-file commit master >raw &&
+	cat raw >forged2 &&
+	echo Qwik | tr "Q" "\000" >>forged2 &&
+	git hash-object -w -t commit forged2 >forged2.commit &&
+	git show --pretty=short --show-signature $(cat forged2.commit) >actual2 &&
+	grep "BAD signature from" actual2 &&
+	! grep "Good signature from" actual2
+'
+
+test_done