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>

builtin/grep.c

@@ -398,7 +398,8 @@ static int grep_cache(struct grep_opt *opt, const struct pathspec *pathspec, int
 		if (cached || (ce->ce_flags & CE_VALID) || ce_skip_worktree(ce)) {
 			if (ce_stage(ce) || ce_intent_to_add(ce))
 				continue;
-			hit |= grep_sha1(opt, ce->sha1, ce->name, 0, ce->name);
+			hit |= grep_sha1(opt, ce->oid.hash, ce->name, 0,
+					 ce->name);
 		}
 		else
 			hit |= grep_file(opt, ce->name);