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>

object-file-convert.c

@@ -56,7 +56,7 @@ static int decode_tree_entry_raw(struct object_id *oid, const char **path,
 		return -1;
 	*len = strlen(*path) + 1;
 
-	oidread_algop(oid, (const unsigned char *)*path + *len, algo);
+	oidread(oid, (const unsigned char *)*path + *len, algo);
 	return 0;
 }