Subject: Re: [PATCH v3 1/2] builtin/config.c: treat type specifiers singularly

From: Taylor Blau <[email-masked]>
Date: Wed, 4 Apr 2018 18:53:04 -0700

On Wed, Apr 04, 2018 at 03:57:12AM -0400, Eric Sunshine wrote:
> On Wed, Apr 4, 2018 at 2:07 AM, Taylor Blau <[email-masked]> wrote:
> > [...]
> > In fact, `git config` will not accept multiple type specifiers at a
> > time, as indicated by:
> >
> >   $ git config --int --bool some.section
> >   error: only one type at a time.
> >
> > This patch uses `OPT_SET_INT` to prefer the _last_ mentioned type
> > specifier, so that the above command would instead be valid, and a
> > synonym of:
> >
> >   $ git config --bool some.section
> >
> > This change is motivated by two urges: (1) it does not make sense to
> > represent a singular type specifier internally as a bitset, only to
> > complain when there are multiple bits in the set. `OPT_SET_INT` is more
> > well-suited to this task than `OPT_BIT` is. (2) a future patch will
> > introduce `--type=<type>`, and we would like not to complain in the
> > following situation:
> >
> >   $ git config --int --type=int
>
> I can understand "last wins" for related options such as "--verbose
> --quiet" or "--verbose=1 --verbose=2", but I have a lot of trouble
> buying the "last wins" argument in this context where there is no
> semantic relationship between, say, --bool and --expiry-date.
> Specifying conflicting options together is likely to be unintentional,
> thus reporting it as an error seems sensible, so I'm not convinced
> that patch's removal of that error is a good idea.
>
> I understand that you're doing this to avoid complaining about "--int
> --type=int", but exactly how that case is supported should be an
> implementation detail; it doesn't need to bleed into the UI as an
> unnecessary and not-well-justified loosening of an age-old
> restriction. There are other ways to support "--int --type=int"
> without "last wins". Also, do we really need to support "--int
> --type=int"? Is that an expected use-case?

This is a fair concern, though I view the problem slightly differently.
I see this change as being motivated by the fact that we are adding
"--type", not removing an age-old restriction.

Peff's motivation for this--as I understand it--is that "--type=int"
should be a _true_ synonym for "--int". Adopting the old-style
"OPT_SET_BIT" for this purpose makes "--type=int" and "--int" _mostly_ a
synonym for one another, except that "--type=bool --type=int" will not
complain, whereas "--bool --int" would.

Loosening this restriction, in my view, brings us closer (1) to the new
semantics of multiple "--type"'s, and (2) to the existing semantics of
"--verbose=1 --verbose=2" as you mentioned above.

I would like to hear Peff's take on this as well, since he suggested the
patch originally, and would likely provide the clearest insight into
this.

Thanks,
Taylor