fetch: don't try to update unfetched tracking refs

Since commit f269048 (fetch: opportunistically update tracking refs,
2013-05-11) we update tracking refs opportunistically when fetching
remote branches.  However, if there is a configured non-pattern refspec
that does not match any of the refspecs given on the command line then a
fatal error occurs.

Fix this by setting the "missing_ok" flag when calling get_fetch_map.

Test-added-by: Jeff King <peff@peff.net>
Signed-off-by: John Keeping <john@keeping.me.uk>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch.c

@@ -183,7 +183,7 @@ static struct ref *get_ref_map(struct transport *transport,
 		old_tail = tail;
 		for (i = 0; i < transport->remote->fetch_refspec_nr; i++)
 			get_fetch_map(ref_map, &transport->remote->fetch[i],
-				      &tail, 0);
+				      &tail, 1);
 		for (rm = *old_tail; rm; rm = rm->next)
 			rm->fetch_head_status = FETCH_HEAD_IGNORE;
 	} else {

t/t5510-fetch.sh

@@ -422,6 +422,22 @@ test_expect_success 'configured fetch updates tracking' '
 	)
 '
 
+test_expect_success 'non-matching refspecs do not confuse tracking update' '
+	cd "$D" &&
+	git update-ref refs/odd/location HEAD &&
+	(
+		cd three &&
+		git update-ref refs/remotes/origin/master base-origin-master &&
+		git config --add remote.origin.fetch \
+			refs/odd/location:refs/remotes/origin/odd &&
+		o=$(git rev-parse --verify refs/remotes/origin/master) &&
+		git fetch origin master &&
+		n=$(git rev-parse --verify refs/remotes/origin/master) &&
+		test "$o" != "$n" &&
+		test_must_fail git rev-parse --verify refs/remotes/origin/odd
+	)
+'
+
 test_expect_success 'pushing nonexistent branch by mistake should not segv' '
 
 	cd "$D" &&