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 <marcandre.lureau@gmail.com>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-svn.perl

@@ -519,7 +519,8 @@ sub cmd_dcommit {
 }
 
 sub cmd_find_rev {
-	my $revision_or_hash = shift;
+	my $revision_or_hash = shift or die "SVN or git revision required ",
+	                                    "as a command-line argument\n";
 	my $result;
 	if ($revision_or_hash =~ /^r\d+$/) {
 		my $head = shift;