Re: [PATCH 2/3] format_config: simplify buffer handling

[Jeff King <peff@peff.net>]

On Fri, Aug 21, 2015 at 10:43:58AM -0700, Junio C Hamano wrote:

> Junio C Hamano <gitster@pobox.com> writes:
> 
> > I wonder if we can do this instead
> >
> > 	if (!omit_values) {
> > -		if (show_keys)
> > +		if (show_keys && value_)
> > 			strbuf_addch(buf, key_delim);
> >
> > though.  That would eliminate the need for rolling back.
> 
> No we cannot.  "config --bool --get-regexp" could get a NULL value_
> and has to turn it to " true".
> 
> Sorry for the noise.

Right, I had the same thought and reached the same conclusion.

By the way, I do not think the rollback by itself is gross, it is just
that it has to reproduce the "show_keys" logic. That is, it _really_
wants to be:

  else {
	  /* nothing to show; rollback delim */
	  if (we_added_delim)
		  strbuf_setlen(buf, buf->len - 1);
  }

and I use "show_keys" as a proxy for "did we add it". Which is
reproducing the logic that you quoted above, and if the two ever get out
of sync, it will be a bug. So you could write it as:

  int we_added_delim = 0;
  if (show_keys) {
	strbuf_addch(buf, key_delim);
	we_added_delim = 1;
  }

I didn't, because it's ugly, and the function is short enough and
unlikely enough to change that it probably won't matter.

You could perhaps also write it as:

  size_t baselen = buf->len;
  if (show_keys)
	strbuf_addch(buf, key_delim);
  ...
  else {
	/* rollback delim */
	strbuf_setlen(buf, baselen);
  }

-Peff