Re: [PATCH v5 1/1] config: add conditional include

[Jeff King <peff@peff.net>]

On Fri, Feb 24, 2017 at 09:46:17AM -0800, Junio C Hamano wrote:

> Duy Nguyen <pclouds@gmail.com> writes:
> 
> >>> +     if (skip_prefix_mem(cond, cond_len, "gitdir:", &cond, &cond_len))
> >>> +             return include_by_gitdir(cond, cond_len, 0);
> >>> +     else if (skip_prefix_mem(cond, cond_len, "gitdir/i:", &cond, &cond_len))
> >>> +             return include_by_gitdir(cond, cond_len, 1);
> >>
> >> This may be OK for now, but it should be trivial to start from a
> >> table with two entries, i.e.
> >>
> >>         struct include_cond {
> >>                 const char *keyword;
> >>                 int (*fn)(const char *, size_t);
> >>         };
> >>
> >> and will show a better way to do things to those who follow your
> >> footsteps.
> >
> > Yeah I don't see a third include coming soon and did not go with that.
> > Let's way for it and refactor then.
> 
> I would have said exactly that in my message if you already had
> include_by_gitdir() and include_by_gitdir_i() as separate functions.
> 
> But I didn't, because the above code gives an excuse to the person
> who adds the third one to be lazy and add another "else if" for
> expediency, because making it table-driven would require an extra
> work to add two wrapper functions that do not have anything to do
> with the third one being added.

I don't think driving that with a two-entry table is the right thing
here. We are as likely to add another "foobar:" entry as we are to add
another modifier "/i" modifier to "gitdir:", and it is unclear whether
that modifier would be mutually exclusive with "/i".

E.g., imagine we add "/re" for a regex, but allow a case-insensitive
regex with an "i", giving something like "gitdir/i/re:".  Now you would
want to drive it by matching "gitdir" first, and then collecting the
"/i/re" independently, to avoid an explosion of matches.

Driving that with a table is much more complex. I'd just as soon keep
things as simple as possible for now and worry about flagging it in
review when something new gets added.

-Peff