git svn: strip leading path when making empty dirs

Since unhandled.log stores paths relative to the repository
root, we need to strip out leading path components if the
directories we're tracking are not the repository root.

Reported-by: Björn Steinbrink
Signed-off-by: Eric Wong <normalperson@yhbt.net>
diff --git a/git-svn.perl b/git-svn.perl
index 7f7a56f..957d44e 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -2752,8 +2752,11 @@
 		}
 	}
 	close $fh;
+
+	my $strip = qr/\A\Q$self->{path}\E(?:\/|$)/;
 	foreach my $d (sort keys %empty_dirs) {
 		$d = uri_decode($d);
+		$d =~ s/$strip//;
 		next if -d $d;
 		if (-e _) {
 			warn "$d exists but is not a directory\n";