fast-import: convert internal structs to struct object_id

fast-import: convert internal structs to struct object_id

Convert struct tree_entry_ms, struct branch, struct tag, and struct
hash_list to use struct object_id by changing the definition and
applying the following semantic patch, plus the standard object_id
transforms:

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

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

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

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

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

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

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

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

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