$oldmode =~ m/^(?:10|12)\d{4}$/;
if ($oldmode =~ m/[^0]/ &&
$newmode =~ m/[^0]/) {
+ # both old and new files exist
die "mode or type changed\n" if $oldmode ne $newmode;
die "modified symlink\n" unless $newmode =~ m/^10/;
+ } elsif ($oldmode =~ m/[^0]/) {
+ # deletion
+ die "non-default mode or type\n"
+ unless $newmode =~ m/^100644$/ ||
+ $oldmode =~ m/^100644$/;
} else {
+ # creation
die "non-default mode or type\n"
unless $newmode =~ m/^100644$/ ||
$oldmode =~ m/^100644$/;