Re: [PATCH 04/10] attr: more matching optimizations from .gitignore

[Nguyen Thai Ngoc Duy <pclouds@gmail.com>]

On Sat, Oct 6, 2012 at 1:48 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes:
>
>> +Unlike `.gitignore`, negative patterns are not supported.
>> +Patterns that match directories are also not supported.
>
> Is "are not supported" the right phrasing?
>
> I think it makes perfect sense not to forbid "!path attr1", because
> it is unclear what it means (e.g. "path -attr1" vs "path !attr1").
> So I would say "Negative patterns are forbidden as they do not make
> any sense".

!path/sub/ alone does not mean anything. It must be used together with
a positive pattern to define the set of paths the same attribute
assignment statement applies to. This makes sense (attr, -attr1 or
!attr1 are all OK):

*.c attr1
!foo.c attr1

But this does not (actually "!foo.c" line has no effects because of
different attribute assignments):

*.c attr1
!foo.c attr2

It could be even more confusing in multiple attribute manipulation:

*.c attr1
*.h -attr2
!foo.[ch] attr1 -attr2

So "not supported" and "forbidden" are equally OK. I just want to
raise a point that it has some use before we go for "forbidden".

> Nguyen Thai Ngoc Duy <pclouds@gmail.com> writes:
>
>> On Sat, Oct 6, 2012 at 12:36 PM, Junio C Hamano <gitster@pobox.com> wrote:
>>>> Or the user might think "path/ attr1" sets attr1 for all files under
>>>> "path/" because it does not make sense to attach attributes to a
>>>> directory in git.
>>>
>>>    ...
>>>
>>>    We may not have a need to assign a real attribute to a directory
>>>    right now, because nothing in Git asks for an attribute for a
>>>    directory. But that does not necessarily mean we would never need a
>>>    way to give an attribute to a directory but not to its contents.
>>
>> Exactly why we should not make "path/ attr" no-op. If we want to make
>> it meaningful some day in future, I don't think we want those no-ops
>> lay around and suddenly cause changes in behavior with a new version
>> of git.
>
> I do not think you understood.  "path/ attr" is a no-op from the
> point of view of the *users* of the current versions of Git.  It is
> perfectly fine to accept and apply attr to "path/"; no codepath in
> Git should be asking about path/ anyway, so it ends up to be a
> no-op.  You shouldn't be erroring out at the syntactic level, i.e.
> when these lines are parsed.

My objection is no-op lines are timed bombs. But users can already do
"dir attr" (no slashes), which is no-op. So yeah, no-op is fine.
-- 
Duy