apply: handle traditional patches with space in filename

apply: handle traditional patches with space in filename

To discover filenames from the --- and +++ lines in a traditional
unified diff, currently "git apply" scans forward for a whitespace
character on each line and stops there.  It can't use the whole line
because "diff -u" likes to include timestamps, like so:

 --- foo	2000-07-12 16:56:50.020000414 -0500
 +++ bar	2010-07-12 16:56:50.020000414 -0500

The whitespace-seeking heuristic works great, even when the tab
has been converted to spaces by some email + copy-and-paste
related corruption.

Except for one problem: if the filename itself contains whitespace,
the inferred filename will be too short.

When Giuseppe ran into this problem, it was for a file creation
patch (for debian/licenses/LICENSE.global BSD-style Chromium).
So one can't use the list of files present in the index to deduce an
appropriate filename (not to mention that way lies madness; see
v0.99~402, 2005-05-31).

Instead, look for a timestamp and use that if present to mark the end
of the filename.  If no timestamp is present, the old heuristic is
used, with one exception: the space character \040 is not considered
terminating whitespace any more unless it is followed by a timestamp.

Reported-by: Giuseppe Iuculano <iuculano@debian.org>
Acked-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>