Re: [PATCH v2] specifying ranges: we did not mean to make ".." an empty set

[Michael J Gruber <git@drmicha.warpmail.net>]

Jeff King venit, vidit, dixit 02.05.2011 23:01:
> On Mon, May 02, 2011 at 01:56:51PM -0700, Junio C Hamano wrote:
> 
>> Either end of revision range operator can be omitted to default to HEAD,
>> as in "origin.." (what did I do since I forked) or "..origin" (what did
>> they do since I forked).  But the current parser interprets ".."  as an
>> empty range "HEAD..HEAD", and worse yet, because ".." does exist on the
>> filesystem, we get this annoying output:
>>
>>   $ cd Documentation/howto
>>   $ git log .. ;# give me recent commits that touch Documentation/ area.
>>   fatal: ambiguous argument '..': both revision and filename
>>   Use '--' to separate filenames from revisions
>>
>> Surely we could say "git log ../" or even "git log -- .." to disambiguate,
>> but we shouldn't have to.
>>
>> Helped-by: Jeff King <peff@peff.net>
>> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> 
> Looks good to me.

I'm sorry but I don't like this at all, because:

> Doing "..." is still allowed, but will never produce any useful results.
> I don't know if it is worth disallowing it to catch errors. I am tempted
> to say it should be magic for "@{u}...HEAD", but I think just "..." is
> getting unreadably magical. "@{u}...HEAD" is already pretty concise and
> is much more readable.

We need to disambiguate any pathspec with "--" which could be a revision
parameter. Therefore I find it very unnatural to disambiguate ".." to a
pathspec automatically (and have "..." error out). "../" is really
simple enough to type.

For "..", we should either catch the error or, better, have ".." default
to "@{u}..HEAD" and do the same for "...". Those are used much more
often, and this goes with "try to parse as a rev first, then pathspec".

Michael