A library for matching files using patterns such as "src/**/*.png" for all .png files recursively under the src directory. Features: All matching is O(n). Most functions precompute some information given only one argument. See System.FilePattern and ?== simple matching and semantics. Use match and substitute to extract suitable strings from the * and ** matches, and substitute them back into other patterns. Use step and matchMany to perform bulk matching of many patterns against many paths simultaneously. Use System.FilePattern.Directory to perform optimised directory traverals using patterns. Originally taken from the Shake library.