tag: recognize rfc1991 signatures

We have always been creating rfc1991 signatures for users with "rfc1991"
in their gpg config but failed to recognize them (tag -l -n largenumber)
and verify them (tag -v, verify-tag).

Make good use of the refactored signature detection and let us recognize
and verify those signatures also.

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

t/t7004-tag.sh

@@ -1048,19 +1048,19 @@ cp "$1" actual
 EOF
 chmod +x fakeeditor
 
-test_expect_failure GPG \
+test_expect_success 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 \
+test_expect_success GPG \
 	'verifying rfc1991 signature' '
 	git tag -v rfc1991-signed-tag
 '
 
-test_expect_failure GPG \
+test_expect_success GPG \
 	'list tag with rfc1991 signature' '
 	echo "rfc1991-signed-tag RFC1991 signed tag" >expect &&
 	git tag -l -n1 rfc1991-signed-tag >actual &&
@@ -1073,12 +1073,12 @@ test_expect_failure GPG \
 
 rm -f gpghome/gpg.conf
 
-test_expect_failure GPG \
+test_expect_success GPG \
 	'verifying rfc1991 signature without --rfc1991' '
 	git tag -v rfc1991-signed-tag
 '
 
-test_expect_failure GPG \
+test_expect_success GPG \
 	'list tag with rfc1991 signature without --rfc1991' '
 	echo "rfc1991-signed-tag RFC1991 signed tag" >expect &&
 	git tag -l -n1 rfc1991-signed-tag >actual &&
@@ -1089,7 +1089,7 @@ test_expect_failure GPG \
 	test_cmp expect actual
 '
 
-test_expect_failure GPG \
+test_expect_success GPG \
 	'reediting a signed tag body omits signature' '
 	echo "RFC1991 signed tag" >expect &&
 	GIT_EDITOR=./fakeeditor git tag -f -s rfc1991-signed-tag $commit &&

tag.c

@@ -5,6 +5,7 @@
 #include "blob.h"
 
 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
+#define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
 
 const char *tag_type = "tag";
 
@@ -140,7 +141,8 @@ size_t parse_signature(const char *buf, unsigned long size)
 {
 	char *eol;
 	size_t len = 0;
-	while (len < size && prefixcmp(buf + len, PGP_SIGNATURE)) {
+	while (len < size && prefixcmp(buf + len, PGP_SIGNATURE) &&
+			prefixcmp(buf + len, PGP_MESSAGE)) {
 		eol = memchr(buf + len, '\n', size - len);
 		len += eol ? eol - (buf + len) + 1 : size - len;
 	}