[BUG] minor: wrong handling of GIT_AUTHOR_DATE

hi

i found a minor bug in the handling of the environment variable GIT_AUTHOR_DATE

i used this variable to import an old project.

i used "stat" to get the timestamp of a file and set the git history to this date with this command:

GIT_AUTHOR_DATE=`stat -c '%y' "$FILE"`

old files (created with an older kernel) produced this output.

2008-05-28 14:21:35.000000000 +0200

but new files return nanosecond resolution timestamps.

2008-06-04 17:25:54.917476713 +0200

of course this resolution is NOT needed for git, but git DOES NOT ignore this time- stamps. it changes the date to something completly wrong :-/

steps to reproduce:

$ git init
$ touch test
$ stat -c %y test
2008-08-16 22:25:45.491701924 +0200
$ export GIT_AUTHOR_DATE=`stat -c %y test`
$ git add test
$ git commit -a
$ git log
commit 56f92b8f6efc7bdaa5abdf03a8c5dbf79dd1fdff
Author: Hermann Gausterer <git-bugreport@mrq1.org>
Date:   Thu Aug 1 01:52:04 1985 +0200

    test
$

mfg hermann