fast-export: report SHA-1 instead of gibberish when marks exist already

Cc: Pieter de Bie <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

builtin/fast-export.c

@@ -644,7 +644,7 @@ static void import_marks(char *input_file)
 			die ("Could not read blob %s", sha1_to_hex(sha1));
 
 		if (object->flags & SHOWN)
-			error("Object %s already has a mark", sha1);
+			error("Object %s already has a mark", sha1_to_hex(sha1));
 
 		mark_object(object, mark);
 		if (last_idnum < mark)