git-svn: fix find-rev error message when missing arg
git-svn: fix find-rev error message when missing arg

Just let the user know that a revision argument is missing instead of
a perl error. This error message mimic the "init" error message, but
could be improved.

Signed-off-by: Marc-Andre Lureau <a6f2b960a4aca61381fc650a67901b2ac8e83e6d@gmail.com>
Acked-by: Eric Wong <8c2951295f8292b0c03727bc4652981172298eae@yhbt.net>
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