Re: [PATCH 05/15] sequencer: lib'ify read_and_refresh_cache()

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <johannes.schindelin@gmx.de> writes:

> To be truly useful, the sequencer should never die() but always return
> an error.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>  sequencer.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)

Instead of dying there, you let the caller high up in the callchain
to notice the error and handle it (by dying).  There are two call
sites of read_and_refresh_cache(), one of which is pick_commits(),
whose callers you already verified that they are prepared to do the
right thing given an "error" return from it when you did 3/15, so
the conversion is safe.  The other one, sequencer_pick_revisions()
is also prepared to relay an error return back to its caller and you
made sure its callers are all safe when you did 3/15.

Good.

> diff --git a/sequencer.c b/sequencer.c
> index b90294f..a8c3a48 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -638,18 +638,21 @@ static int prepare_revs(struct replay_opts *opts)
>  	return 0;
>  }
>  
> -static void read_and_refresh_cache(struct replay_opts *opts)
> +static int read_and_refresh_cache(struct replay_opts *opts)
>  {
>  	static struct lock_file index_lock;
>  	int index_fd = hold_locked_index(&index_lock, 0);
>  	if (read_index_preload(&the_index, NULL) < 0)
> -		die(_("git %s: failed to read the index"), action_name(opts));
> +		return error(_("git %s: failed to read the index"),
> +			action_name(opts));
>  	refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
>  	if (the_index.cache_changed && index_fd >= 0) {
>  		if (write_locked_index(&the_index, &index_lock, COMMIT_LOCK))
> -			die(_("git %s: failed to refresh the index"), action_name(opts));
> +			return error(_("git %s: failed to refresh the index"),
> +				action_name(opts));
>  	}
>  	rollback_lock_file(&index_lock);
> +	return 0;
>  }
>  
>  static int format_todo(struct strbuf *buf, struct commit_list *todo_list,
> @@ -977,7 +980,8 @@ static int pick_commits(struct commit_list *todo_list, struct replay_opts *opts)
>  	if (opts->allow_ff)
>  		assert(!(opts->signoff || opts->no_commit ||
>  				opts->record_origin || opts->edit));
> -	read_and_refresh_cache(opts);
> +	if (read_and_refresh_cache(opts))
> +		return -1;
>  
>  	for (cur = todo_list; cur; cur = cur->next) {
>  		save_todo(cur, opts);
> @@ -1041,7 +1045,8 @@ int sequencer_pick_revisions(struct replay_opts *opts)
>  	if (opts->subcommand == REPLAY_NONE)
>  		assert(opts->revs);
>  
> -	read_and_refresh_cache(opts);
> +	if (read_and_refresh_cache(opts))
> +		return -1;
>  
>  	/*
>  	 * Decide what to do depending on the arguments; a fresh