t/t7004-tag: test handling of rfc1991 signatures

Currently, git expects "-----BEGIN PGP SIGNATURE-----" at the beginning of a
signature. But gpg uses "MESSAGE" instead of "SIGNATURE" when used with
the "rfc1991" option. This leads to git's failing to verify it's own
signed tags, among other problems.

Add tests for all code paths (tag -v, tag -l -n largenumber, tag -f
without -m) where signature detection matters.

Reported-by: Stephan Hugel <urschrei@gmail.com>
Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7004-tag.sh

@@ -1030,6 +1030,72 @@ test_expect_success GPG \
 	test_cmp expect actual
 '
 
+# usage with rfc1991 signatures
+echo "rfc1991" > gpghome/gpg.conf
+get_tag_header rfc1991-signed-tag $commit commit $time >expect
+echo "RFC1991 signed tag" >>expect
+echo '-----BEGIN PGP MESSAGE-----' >>expect
+test_expect_success GPG \
+	'creating a signed tag with rfc1991' '
+	git tag -s -m "RFC1991 signed tag" rfc1991-signed-tag $commit &&
+	get_tag_msg rfc1991-signed-tag >actual &&
+	test_cmp expect actual
+'
+
+cat >fakeeditor <<'EOF'
+#!/bin/sh
+cp "$1" actual
+EOF
+chmod +x fakeeditor
+
+test_expect_failure GPG \
+	'reediting a signed tag body omits signature' '
+	echo "RFC1991 signed tag" >expect &&
+	GIT_EDITOR=./fakeeditor git tag -f -s rfc1991-signed-tag $commit &&
+	test_cmp expect actual
+'
+
+test_expect_failure GPG \
+	'verifying rfc1991 signature' '
+	git tag -v rfc1991-signed-tag
+'
+
+test_expect_failure GPG \
+	'list tag with rfc1991 signature' '
+	echo "rfc1991-signed-tag RFC1991 signed tag" >expect &&
+	git tag -l -n1 rfc1991-signed-tag >actual &&
+	test_cmp expect actual &&
+	git tag -l -n2 rfc1991-signed-tag >actual &&
+	test_cmp expect actual &&
+	git tag -l -n999 rfc1991-signed-tag >actual &&
+	test_cmp expect actual
+'
+
+rm -f gpghome/gpg.conf
+
+test_expect_failure GPG \
+	'verifying rfc1991 signature without --rfc1991' '
+	git tag -v rfc1991-signed-tag
+'
+
+test_expect_failure GPG \
+	'list tag with rfc1991 signature without --rfc1991' '
+	echo "rfc1991-signed-tag RFC1991 signed tag" >expect &&
+	git tag -l -n1 rfc1991-signed-tag >actual &&
+	test_cmp expect actual &&
+	git tag -l -n2 rfc1991-signed-tag >actual &&
+	test_cmp expect actual &&
+	git tag -l -n999 rfc1991-signed-tag >actual &&
+	test_cmp expect actual
+'
+
+test_expect_failure GPG \
+	'reediting a signed tag body omits signature' '
+	echo "RFC1991 signed tag" >expect &&
+	GIT_EDITOR=./fakeeditor git tag -f -s rfc1991-signed-tag $commit &&
+	test_cmp expect actual
+'
+
 # try to sign with bad user.signingkey
 git config user.signingkey BobTheMouse
 test_expect_success GPG \