git-svn: avoid fetching files outside of the URL we're tracking

Thanks to Santi <sbejar@gmail.com> for the bug report and explanation:
> /path/to/repository/project/file
> /path/to/repository/project-2/file
<...>
> you end up with a project with the following files:
>
> file
> -2/file

Signed-off-by: Eric Wong <normalperson@yhbt.net>

contrib/git-svn/git-svn.perl

@@ -2617,7 +2617,7 @@ sub libsvn_connect {
 sub libsvn_get_file {
 	my ($gui, $f, $rev) = @_;
 	my $p = $f;
-	return unless ($p =~ s#^\Q$SVN_PATH\E/?##);
+	return unless ($p =~ s#^\Q$SVN_PATH\E/##);
 
 	my ($hash, $pid, $in, $out);
 	my $pool = SVN::Pool->new;