[PATCH] cat-file: be consistent in usage string and documentation.

Now that we have something called tag object, and a notion of
"tags" stored in .git/refs/tags/ directory, the word "tagname"
has become misleading in the usage string.  The documentation
already calls that <type>.
Signed-off-by: NJunio C Hamano <junkio@cox.net>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

cat-file.c

@@ -13,7 +13,7 @@ int main(int argc, char **argv)
 	unsigned long size;
 
 	if (argc != 3 || get_sha1(argv[2], sha1))
-		usage("git-cat-file [-t | -s | tagname] <sha1>");
+		usage("git-cat-file [-t | -s | <type>] <sha1>");
 
 	if (!strcmp("-t", argv[1]) || !strcmp("-s", argv[1])) {
 		if (!sha1_object_info(sha1, type,