Re: [RFC PATCH 0/4] pathspec labels [WAS: submodule groups]

[Stefan Beller <sbeller@google.com>]

On Mon, May 16, 2016 at 3:02 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Stefan Beller <sbeller@google.com> writes:
>
>>> Hmph, why not?
>>
>> We need a namespace for which
>> * we can guarantee that it is for labeling purposes only (even in the future)
>> * is obvious to the user to be a labeling name space
>>
>> Starting with "label" offers both?
>
> Ah, of course.  I thought that you were trying to limit ":(attr:<attribute>)"
> magic only to attributes that begin with "label-", which is where my
> "why not?" comes from.

And going by the logic you presented before, we would
need to error out for the given pathspec ":(<string>)" if

* either the string is not well known (e.g. diif, eol )
* or is outside of the labeling namespace.

So we don't want to see users complaining about
"bug attr:foo worked as a label, now it is a feature; you broke my code"

We would need to ignore data from .gitattributes as it may be crafted from
a newer version of Git, but the command line argument still needs to die
for unknown arguments?

So asking for :(foo) would yield a

    fatal: attr 'foo' is not known to Git, nor is it in the labeling name space

I guess what I am asking is if there is a nice way to query "do we know
this attribute?"

Stefan