Merge branch 'ab/reverse-midx-optim' into maint

The code that optionally creates the *.rev reverse index file has
been optimized to avoid needless computation when it is not writing
the file out.

* ab/reverse-midx-optim:
  pack-write: skip *.rev work when not writing *.rev

pack-write.c

@@ -222,6 +222,9 @@ const char *write_rev_file(const char *rev_name,
 	uint32_t i;
 	const char *ret;
 
+	if (!(flags & WRITE_REV) && !(flags & WRITE_REV_VERIFY))
+		return NULL;
+
 	ALLOC_ARRAY(pack_order, nr_objects);
 	for (i = 0; i < nr_objects; i++)
 		pack_order[i] = i;