Re: [WIP PATCH 0/5] support --exclude for diff/log commands

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Mar 10, 2011, 10:05 UTC
Message-ID: <AANLkTimsv9bO+Go6Mqrrp_1-AZ=sC3ndyAuskPYLVbkv@mail.gmail.com>
In-Reply-To: <7vvczr5pw6.fsf@alter.siamese.dyndns.org>

2011/3/10 Junio C Hamano <gitster@pobox.com>:

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> Let's step back a bit.
>
> We chose to use ":/<regexp>" as one new form of extended SHA-1 expression
> to name an object for two reasons: (1) no normal <ref> can have a colon in
> it, because of check-ref-format restriction; (2) ":" is an unlikely letter
> to appear at the beginning of a pathname, and people with such a path can
> work around by saying "./:frotz" or "\:xyzzy".
>
> There is a disambiguation logic to check a list of arguments that lacks an
> explicit "--" separator to make sure that each element early on the list
> can only be interpreted as an object name but not as a pathname that
> exists on the filesystem, and all the remaining elements are pathnames
> that exist on the filesystem.
>
> If we introduce an extended syntax for pathspec and make the prefix magic
> character ":", and if we choose to use ":/" as one kind of magic, I was a
> bit worried that this may affect the disambiguation.  The users must use
> an explicit "--" when feeding a pathspec with the magic so that the parser
> knows which kind of magic (either object name magic or pathspec magic)
> they are talking about.

Or.. we can consider this ':' a special form of wildcard and interpret the same way:

 - first try exact match. If it matches, the leading ':' is
interpreted literally as part of file name.
 - magic.

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> I however realized that it is not an issue at all, because the users
> already need to disambiguate with "--" when using wildcards in their
> pathspecs (e.g. "git log 'Makefil*'" will give you an ambiguity error).
> Admittedly, wildcard pathspecs are lessor kind of magic, but they are
> magic nevertheless.

Yes, ':' is on the same side with wildcard pathspecs.

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> So my tentative conclusion is that there is no problem using the same ":"
> as the magic introducer for pathspecs, just like we do for object names.
>
>        Side note: please point out flaws in the above train of thought
>        that would make the end result non-workable.

Huh? I failed.

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> I am not very happy with ":!" as negative from syntactical point of view,
> because traditionally "!" is a tad cumbersome to quote in shells with
> history support (e.g. "csh"), but unfortunately I don't think of any good
> alternative that is easy to type.  Pathspecs are globs by nature, and "!"
> is a good choice of nagation indicator for that reason (think "[!aeiou]"
> not "[^aeiou]" the latter of which is a regexp and not glob), though.

We don't need to stick to ':!'. I just needed something to start coding. Other candidates can be '^' or '-' or '~'. '^' looks best in my opinion.

-- 
Duy