rebase -i: use struct object_id when writing state

Rather than passing a string around pass the struct object_id that the
string was created from call oid_hex() when we write the file.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rebase.c

@@ -296,7 +296,8 @@ static int get_revision_ranges(struct commit *upstream, struct commit *onto,
 }
 
 static int init_basic_state(struct replay_opts *opts, const char *head_name,
-			    struct commit *onto, const char *orig_head)
+			    struct commit *onto,
+			    const struct object_id *orig_head)
 {
 	FILE *interactive;
 
@@ -340,7 +341,7 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
 
 	if (init_basic_state(&replay,
 			     opts->head_name ? opts->head_name : "detached HEAD",
-			     opts->onto, head_hash)) {
+			     opts->onto, &opts->orig_head)) {
 		free(revisions);
 		free(shortrevisions);
 

sequencer.c

@@ -2692,7 +2692,7 @@ static void write_strategy_opts(struct replay_opts *opts)
 }
 
 int write_basic_state(struct replay_opts *opts, const char *head_name,
-		      struct commit *onto, const char *orig_head)
+		      struct commit *onto, const struct object_id *orig_head)
 {
 	if (head_name)
 		write_file(rebase_path_head_name(), "%s\n", head_name);
@@ -2700,7 +2700,8 @@ int write_basic_state(struct replay_opts *opts, const char *head_name,
 		write_file(rebase_path_onto(), "%s\n",
 			   oid_to_hex(&onto->object.oid));
 	if (orig_head)
-		write_file(rebase_path_orig_head(), "%s\n", orig_head);
+		write_file(rebase_path_orig_head(), "%s\n",
+			   oid_to_hex(orig_head));
 
 	if (opts->quiet)
 		write_file(rebase_path_quiet(), "%s", "");

sequencer.h

@@ -227,7 +227,7 @@ int read_author_script(const char *path, char **name, char **email, char **date,
 		       int allow_missing);
 void parse_strategy_opts(struct replay_opts *opts, char *raw_opts);
 int write_basic_state(struct replay_opts *opts, const char *head_name,
-		      struct commit *onto, const char *orig_head);
+		      struct commit *onto, const struct object_id *orig_head);
 void sequencer_post_commit_cleanup(struct repository *r, int verbose);
 int sequencer_get_last_command(struct repository* r,
 			       enum replay_action *action);