Re: What's cooking in git.git (Oct 2012, #01; Tue, 2)

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Oct 4, 2012, 01:56 UTC
Message-ID: <CACsJy8CAGaEzGZBJq7pOW_2SDpRDLiPqJK0t2WjpuNqLU+yewQ@mail.gmail.com>
In-Reply-To: <7vbogj5sji.fsf@alter.siamese.dyndns.org>

On Thu, Oct 4, 2012 at 1:17 AM, Junio C Hamano <gitster@pobox.com> wrote:

Show 7 quoted lines

> For the double-star at the beginning, you should just turn it into "**/"
> if it is not followed by a slash internally, I think.
>
> What is the semantics of ** in the first place?  Is it described to
> a reasonable level of detail in the documentation updates?  For
> example does "**foo" match "afoo", "a/b/foo", "a/bfoo", "a/foo/b",
> "a/bfoo/c"?  Does "x**y" match "xy", "xay", "xa/by", "x/a/y"?

It's basically what rsync describes: use ’**’ to match anything, including slashes.

Reading rsync's man page again, I notice I missed two other rules related to **:

 - If the pattern contains a / (not counting a trailing /) or a "**",
then it is matched against the full pathname, including any leading
directories.  If  the  pattern  doesn't contain  a / or a "**", then
it is matched only against the final component of the filename.
(Remember that the algorithm is applied recursively so "full filename"
can actually be any portion of a path from the starting directory on
down.)

 - A trailing "dir_name/***" will match both the directory (as if
"dir_name/" had been specified) and everything in the directory (as if
"dir_name/**" had been specified).  This behavior was added in version
2.6.7.

From what you wrote, I think we'll go with the first rule. The second rule looks irrelevant to what git's doing.

> I am guessing that the only sensible definition is that "**"
> requires anything that comes before it (if exists) is at a proper
> hierarchy boundary, and anything matches it is also at a proper
> hierarchy boundary, so "x**y" matches "x/a/y"

and "x/y" too? (As opposed to "x/**/y" which does not)

> and not "xy", "xay",
> nor "xa/by" in the above example.  If "x**y" can match "xy" or "xay"
> (or "**foo" can match "afoo"), it would be unreasonable to say it
> implies the pattern is anchored at any level, no?

Yeah. That makes things easier to reason, though not exactly what we're having.

-- 
Duy