sha1_file: convert index_path to struct object_id

Convert all remaining callers as well.

Signed-off-by: Patryk Obara <patryk.obara@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/notes-merge.c b/notes-merge.c
index c12b354..744c685 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -709,7 +709,7 @@ int notes_merge_commit(struct notes_merge_options *o,
 		/* write file as blob, and add to partial_tree */
 		if (stat(path.buf, &st))
 			die_errno("Failed to stat '%s'", path.buf);
-		if (index_path(blob_oid.hash, path.buf, &st, HASH_WRITE_OBJECT))
+		if (index_path(&blob_oid, path.buf, &st, HASH_WRITE_OBJECT))
 			die("Failed to write blob object from '%s'", path.buf);
 		if (add_note(partial_tree, &obj_oid, &blob_oid, NULL))
 			die("Failed to add resolved note '%s' to notes tree",