Support unraring source files

pkgs/tools/archivers/unrar/default.nix

@@ -23,6 +23,8 @@ stdenv.mkDerivation {
         $out/share/doc/unrar
   '';
 
+  setupHook = ./setup-hook.sh;
+
   meta = with stdenv.lib; {
     description = "Utility for RAR archives";
     homepage = http://www.rarlab.com/;

pkgs/tools/archivers/unrar/setup-hook.sh

@@ -0,0 +1,5 @@
+unpackCmdHooks+=(_tryUnrar)
+_tryUnrar() {
+    if ! [[ "$curSrc" =~ \.rar$ ]]; then return 1; fi
+    unrar x "$curSrc" >/dev/null
+}