tag.c: Parse tagger date (if present)

Just like with committer dates, we parse the tagger date into the
struct tag so its available for further downstream processing.
However since the tagger header was not introduced until Git 0.99.1
we must consider it optional.  For tags missing this header we use
the default date of 0.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

tag.c

@@ -36,6 +36,23 @@ struct tag *lookup_tag(const unsigned char *sha1)
         return (struct tag *) obj;
 }
 
+static unsigned long parse_tag_date(const char *buf, const char *tail)
+{
+	const char *dateptr;
+
+	while (buf < tail && *buf++ != '>')
+		/* nada */;
+	if (buf >= tail)
+		return 0;
+	dateptr = buf;
+	while (buf < tail && *buf++ != '\n')
+		/* nada */;
+	if (buf >= tail)
+		return 0;
+	/* dateptr < buf && buf[-1] == '\n', so strtoul will stop at buf-1 */
+	return strtoul(dateptr, NULL, 10);
+}
+
 int parse_tag_buffer(struct tag *item, void *data, unsigned long size)
 {
 	unsigned char sha1[20];
@@ -86,6 +103,11 @@ int parse_tag_buffer(struct tag *item, void *data, unsigned long size)
 	item->tag = xmemdupz(bufptr, nl - bufptr);
 	bufptr = nl + 1;
 
+	if (!prefixcmp(bufptr, "tagger "))
+		item->date = parse_tag_date(bufptr, tail);
+	else
+		item->date = 0;
+
 	return 0;
 }
 

tag.h

@@ -9,6 +9,7 @@ struct tag {
 	struct object object;
 	struct object *tagged;
 	char *tag;
+	unsigned long date;
 };
 
 extern struct tag *lookup_tag(const unsigned char *sha1);