Re: Fwd: Possibly nicer pathspec syntax?

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, Feb 7, 2017 at 6:42 PM, Junio C Hamano <gitster@pobox.com> wrote:
>
>  1. I think some commands limit their operands to cwd and some work
>     on the whole tree when given no pathspec. I think the "no
>     positive?  then let's give you everything except these you
>     excluded" should base the definition of "everything" to that.
>     IOW, "cd t && git grep -e foo" shows everything in t/ directory,
>     so the default you would add would be "." for "grep"; "cd t &&
>     git diff HEAD~100 HEAD" would show everything, so you would give
>     ":(top)." for "diff".

No. The thing is, "git diff" is relative too - for path
specifications. And the negative entries are pathspecs - and they act
as relative ones.

IOW, that whole

  cd drivers
  git diff A..B -- net/

will actually show the diff for drivers/net - so the pathspec very
much acts as relative to the cwd.

So no, absolute (ie ":(top)" or ":/") doesn't actually make sense for
"diff" either, even though diff by default is absolute when not given
a pathname at all.

But if you do

  cd drivers
  git diff A..B -- :^/arch

then suddenly an absolute positive root _does_ make sense,. because
now the negative pathspec was absolute..

Odd? Yes it is. But the positive pathspec rules are what they are, and
they are actually what I suspect everybody really wants. The existing
negative ones match the rules for the positive ones.

So I suspect that the best thing is if the "implicit positive rule
when there are no explicit ones" ends up matching the same semantics
as the (explicit) negative entries have..

>  2. I am not sure what ctype.c change is about.  Care to elaborate?

I didn't see the need for it either until I made the rest of the
patch, and it didn't work at all.

The pathspec.c code uses "if (is_pathspec_magic(..))" to test whether
a character is a short magiic pathspec character.  But '^' wasn't in
that set, because it was already marked as being (only) in the regex
set.

Does that whole is_pathspec_magic() thing make any sense when we have
an array that specifies the special characters we react to? No it does
not.

But it is what the code does, and I just made that code work.

>  3. I think our recent trend is to wean ourselves away from "an
>     empty element in pathspec means all paths match", and I think we
>     even have accepted a patch to emit a warning.  Doesn't the
>     warning trigger for the new code below?

It didn't trigger for me in my testing, I suspect the warning is at an
earlier level when it walks through the argv[] array and fills in the
pathspec arrays. But I didn't actually look for it.

                   Linus