Merge branch 'rs/pack-objects-no-unnecessary-realloc' into maint

"git pack-objects" unnecessarily copied the previous contents when
extending the hashtable, even though it will populate the table
from scratch anyway.

* rs/pack-objects-no-unnecessary-realloc:
  pack-objects: use free()+xcalloc() instead of xrealloc()+memset()

pack-objects.c

@@ -47,8 +47,8 @@ static void rehash_objects(struct packing_data *pdata)
 	if (pdata->index_size < 1024)
 		pdata->index_size = 1024;
 
-	pdata->index = xrealloc(pdata->index, sizeof(uint32_t) * pdata->index_size);
-	memset(pdata->index, 0, sizeof(int) * pdata->index_size);
+	free(pdata->index);
+	pdata->index = xcalloc(pdata->index_size, sizeof(*pdata->index));
 
 	entry = pdata->objects;