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

[Stefan Beller <sbeller@google.com>]

On Tue, Mar 7, 2017 at 12:47 AM, Jeff King <peff@peff.net> wrote:
> On Mon, Mar 06, 2017 at 02:44:27PM -0800, Stefan Beller wrote:
>
>> > +static int include_condition_is_true(const char *cond, size_t cond_len)
>> > +{
>> ...
>> > +
>> > +       error(_("unrecognized include condition: %.*s"), (int)cond_len, cond);
>> > +       /* unknown conditionals are always false */
>> > +       return 0;
>> > +}
>>
>> Thanks for putting an error message here. I was looking at what
>> is currently queued as origin/nd/conditional-config-include,
>> which doesn't have this error()  (yet / not any more?)
>
> It's "not any more". It was in the original and I asked for it to be
> removed during the last review.

Okay. The joys of contradicting opinions on a mailing list. :)

>
>> I'd strongly suggest to keep the error message here as that way
>> a user can diagnose e.g. a typo in the condition easily.
>>
>> If we plan to extend this list of conditions in the future, and a user
>> switches between versions of git, then they may see this message
>> on a regular basis (whenever they use the 'old' version).
>
> That would make it unlike the rest of the config-include mechanism
> (which quietly ignores things it doesn't understand, like include.foo,
> or include.foo.path), as well as the config code in general (which
> ignores misspelt keys).
>
> Some of that "quiet when you don't understand it" is historical
> necessity. Older versions _can't_ complain about not knowing
> include.path, because they don't yet know it's worth complaining about.

agreed

> Likewise here, if this ships in v2.13 and a new condition "foo:" ships
> in v2.14, you get:
>
>   v2.12 - no complaint; we don't even understand includeIf at all
>   v2.13 - complain; we know includeIf, but not "foo:"
>   v2.14 - works as expected
>
> Which is kind of weird and inconsistent. But maybe the typo-detection
> case is more important to get right than consistency across historical
> versions.

Oh, I see. I was contemplating a future in which 2.12 is not used anymore.

When looking at other examples, such as url.<...>.insteadOf we also do not
warn about typos (well we can't actually).

In diff.<driver>.(command/binary/..) we know the limited set of drivers,
which is similar to the situation we have here.

Maybe a compromise between typo checking (edit distance < 2 -> warn;
silent for larger distances) and the consistency over time is desired.
But this is even more code to write.

So for now I retract my strong opinion and be happy with what is
presented as-is for the reasons Peff gave.

Thanks,
Stefan