archive: convert write_archive_entry_fn_t to object_id

Convert the write_archive_entry_fn_t type to use a pointer to struct
object_id.  Convert various static functions in the tar and zip
archivers also.

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

archive.h

@@ -31,7 +31,7 @@ extern void init_tar_archiver(void);
 extern void init_zip_archiver(void);
 
 typedef int (*write_archive_entry_fn_t)(struct archiver_args *args,
-					const unsigned char *sha1,
+					const struct object_id *oid,
 					const char *path, size_t pathlen,
 					unsigned int mode);