Re: [RFC PATCH v1 1/2] pathspec: warn: long and short forms are incompatible

[Stavros Ntentos <stdedos@gmail.com>]

> We avoid using variable-length arrays in our codebase. ...

Hear hear, however, I wanted to avoid the "small mess"
that allocate/free would cause (one or more of ++sloc, labels, if-nesting); ...

> But two, they are limited in size and the failure mode is not graceful. ...
... however, my main issue is that - I don't know what's a sane allocation size.

> ... The "4096" is scary here ...
While scary, it is "a safe" upper high.
The first time the string ends up in pathspec.c for processing it's here:
	entry = argv[i];
which comes from here
	parse_pathspec(pathspec, magic_mask, flags, prefix, parsed_file.v);

and I don't know what's the maximum size of `parsed_file.v[0]`

> Is this "%4096[^)]" actually valid? I don't think scanf understands
> regular expressions.

I was suprised too - but it's not regex.

see: https://www.cplusplus.com/reference/cstdio/scanf/#parameters - 4th/3rd row from the end

%s is greedy and there would be no other way to limit `sscanf` to not include `)` on its first variable.

> ... though I'm not sure I understand what that is looking for ...

I think it will help you see what I am trying to achieve if you read at the warning message / testcase
https://lore.kernel.org/git/20210326024005.26962-2-stdedos+git@gmail.com/#iZ30t:t6132-pathspec-exclude.sh

And, to clean up the testcase:
	git log --oneline --format=%s -- ':!(glob)**/file'

I guess it should be now obvious what am I targetting:

If someone naively mixes short and long pathspec magics (`!`, and `(glob)`),
short form takes precedence and ignores long magic / assumes long magic as part of path.

(If it's not obvious, all the more reason to include such warning)