allow empty lost+found directory in target directory

mmdebstrap

@@ -1616,14 +1616,35 @@ sub main() {
 	    if (!-d $options->{root}) {
 		die "$options->{root} exists and is not a directory";
 	    }
-	    opendir(my $dh, $options->{root}) or die "Can't opendir($options->{root}): $!";
-	    # Attempt reading the directory thrice. If the third time succeeds,
-	    # then it has more entries than just "." and ".." and must thus not
-	    # be empty.
-	    readdir $dh;
-	    readdir $dh;
+	    # check if the directory is empty or contains nothing more than an
+	    # empty lost+found directory. The latter exists on freshly created
+	    # ext3 and ext4 partitions.
 	    # rationale for requiring an empty directory: https://bugs.debian.org/833525
-	    die "$options->{root} is not empty" if (readdir $dh);
+	    opendir(my $dh, $options->{root}) or die "Can't opendir($options->{root}): $!";
+	    while (my $entry = readdir $dh) {
+		# skip the "." and ".." entries
+		next if $entry eq ".";
+		next if $entry eq "..";
+		# if the entry is a directory named "lost+found" then skip it
+		# if it's empty
+		if ($entry eq "lost+found" and -d "$options->{root}/$entry") {
+		    opendir(my $dh2, "$options->{root}/$entry");
+		    # Attempt reading the directory thrice. If the third time
+		    # succeeds, then it has more entries than just "." and ".."
+		    # and must thus not be empty.
+		    readdir $dh2;
+		    readdir $dh2;
+		    # rationale for requiring an empty directory:
+		    # https://bugs.debian.org/833525
+		    if (readdir $dh2) {
+			die "$options->{root} contains a non-empty lost+found directory";
+		    }
+		    closedir($dh2);
+		} else {
+		    die "$options->{root} is not empty";
+		}
+	    }
+	    closedir($dh);
 	} else {
 	    make_path($options->{root}) or die "cannot create root: $!";
 	}