Remove get_object_hash.

Convert all instances of get_object_hash to use an appropriate reference
to the hash member of the oid member of struct object.  This provides no
functional change, as it is essentially a macro substitution.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jeff King <peff@peff.net>
diff --git a/wt-status.c b/wt-status.c
index 0b5c163..82b87c1 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -1347,7 +1347,7 @@
 	    (!hashcmp(cb.nsha1, sha1) ||
 	     /* perhaps sha1 is a tag, try to dereference to a commit */
 	     ((commit = lookup_commit_reference_gently(sha1, 1)) != NULL &&
-	      !hashcmp(cb.nsha1, get_object_hash(commit->object))))) {
+	      !hashcmp(cb.nsha1, commit->object.oid.hash)))) {
 		const char *from = ref;
 		if (!skip_prefix(from, "refs/tags/", &from))
 			skip_prefix(from, "refs/remotes/", &from);