Git.pm: correctly handle directory name that evaluates to "false"
Git.pm: correctly handle directory name that evaluates to "false"

The repository constructor mistakenly rewrote a Directory parameter that
Perl happens to evaluate to false (e.g. "0") to ".".

Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git