cache: convert struct cache_entry to use struct object_id

Convert struct cache_entry to use struct object_id by applying the
following semantic patch and the object_id transforms from contrib, plus
the actual change to the struct:

@@
struct cache_entry E1;
@@
- E1.sha1
+ E1.oid.hash

@@
struct cache_entry *E1;
@@
- E1->sha1
+ E1->oid.hash

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/helper/test-dump-split-index.c

@@ -23,7 +23,7 @@ int cmd_main(int ac, const char **av)
 	for (i = 0; i < the_index.cache_nr; i++) {
 		struct cache_entry *ce = the_index.cache[i];
 		printf("%06o %s %d\t%s\n", ce->ce_mode,
-		       sha1_to_hex(ce->sha1), ce_stage(ce), ce->name);
+		       oid_to_hex(&ce->oid), ce_stage(ce), ce->name);
 	}
 	printf("replacements:");
 	if (si->replace_bitmap)