Contract a filename, based on a relative path.
There is no corresponding
makeAbsolute function, instead use
System.Directory.canonicalizePath which has the same effect.
Valid y => equalFilePath x y || (isRelative x && makeRelative y x == x) || equalFilePath (y </> makeRelative y x) x
makeRelative x x == "."
null y || equalFilePath (makeRelative x (x </> y)) y || null (takeFileName x)
Windows: makeRelative "C:/Home" "c:/home/bob" == "bob"
Windows: makeRelative "C:/Home" "D:/Home/Bob" == "D:/Home/Bob"
Windows: makeRelative "C:/Home" "C:Home/Bob" == "C:Home/Bob"
Windows: makeRelative "/Home" "/home/bob" == "bob"
Posix: makeRelative "/Home" "/home/bob" == "/home/bob"
Posix: makeRelative "/home/" "/home/bob/foo/bar" == "bob/foo/bar"
Posix: makeRelative "/fred" "bob" == "bob"
Posix: makeRelative "/file/test" "/file/test/fred" == "fred"
Posix: makeRelative "/file/test" "/file/test/fred/" == "fred/"
Posix: makeRelative "some/path" "some/path/a/b/c" == "a/b/c"