hash: require hash algorithm in oidread() and oidclr()

Both `oidread()` and `oidclr()` use `the_repository` to derive the hash
function that shall be used. Require callers to pass in the hash
algorithm to get rid of this implicit dependency.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -1552,7 +1552,7 @@ static void fetch_symref(const char *path, char **symref, struct object_id *oid)
 	free(url);
 
 	FREE_AND_NULL(*symref);
-	oidclr(oid);
+	oidclr(oid, the_repository->hash_algo);
 
 	if (buffer.len == 0)
 		return;