Add readlink (#377)

Fixes #376

release.nix

@@ -1,6 +1,4 @@
 let
-  ghc822 = import ./default.nix { compiler = "ghc822"; };
-
   default = import ./default.nix { };
 
 in
@@ -9,8 +7,6 @@ in
         { name = "all";
 
           constituents = [
-            ghc822.turtle
-
             default.turtle
           ];
         };

src/Turtle/Prelude.hs

@@ -121,6 +121,7 @@ module Turtle.Prelude (
     , cd
     , pwd
     , home
+    , readlink
     , realpath
     , mv
     , mkdir
@@ -943,6 +944,14 @@ pwd = liftIO Filesystem.getWorkingDirectory
 home :: MonadIO io => io FilePath
 home = liftIO Filesystem.getHomeDirectory
 
+-- | Get the path pointed to by a symlink
+readlink :: MonadIO io => FilePath -> io FilePath
+readlink =
+      fmap Filesystem.decodeString
+    . liftIO
+    . System.Directory.getSymbolicLinkTarget
+    . Filesystem.encodeString
+
 -- | Canonicalize a path
 realpath :: MonadIO io => FilePath -> io FilePath
 realpath path = liftIO (Filesystem.canonicalizePath path)

turtle.cabal

@@ -7,7 +7,6 @@ License-File: LICENSE
 Copyright: 2015 Gabriel Gonzalez
 Author: Gabriel Gonzalez
 Maintainer: [email protected]
-Tested-With: GHC == 7.10.2, GHC == 8.0.1
 Bug-Reports: https://github.com/Gabriel439/Haskell-Turtle-Library/issues
 Synopsis: Shell programming, Haskell-style
 Description: @turtle@ is a reimplementation of the Unix command line environment
@@ -55,7 +54,7 @@ Library
         bytestring           >= 0.9.1.8 && < 0.11,
         clock                >= 0.4.1.2 && < 0.9 ,
         containers           >= 0.5.0.0 && < 0.7 ,
-        directory            >= 1.0.7   && < 1.4 ,
+        directory            >= 1.3.1.0 && < 1.4 ,
         exceptions           >= 0.4     && < 0.11,
         foldl                >= 1.1     && < 1.5 ,
         hostname                           < 1.1 ,