Implement `-P` flag from tree

[psyrendust]

-P pattern
        List  only  those  files that match the wild-card pattern.  Note: you must use the -a option to also consider those files beginning with a dot `.'  for
        matching.  Valid wildcard operators are `*' (any zero or more characters), `?' (any single character), `[...]' (any  single  character  listed  between
        brackets  (optional  - (dash) for character range may be used: ex: [A-Z]), and `[^...]' (any single character not listed in brackets) and `|' separates
        alternate patterns.