Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10'

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

third_party/nix/corepkgs/unpack-channel.nix

@@ -0,0 +1,39 @@
+with import <nix/config.nix>;
+
+let
+
+  builder = builtins.toFile "unpack-channel.sh"
+    ''
+      mkdir $out
+      cd $out
+      xzpat="\.xz\$"
+      gzpat="\.gz\$"
+      if [[ "$src" =~ $xzpat ]]; then
+        ${xz} -d < $src | ${tar} xf - ${tarFlags}
+      elif [[ "$src" =~ $gzpat ]]; then
+        ${gzip} -d < $src | ${tar} xf - ${tarFlags}
+      else
+        ${bzip2} -d < $src | ${tar} xf - ${tarFlags}
+      fi
+      if [ * != $channelName ]; then
+        mv * $out/$channelName
+      fi
+    '';
+
+in
+
+{ name, channelName, src }:
+
+derivation {
+  system = builtins.currentSystem;
+  builder = shell;
+  args = [ "-e" builder ];
+  inherit name channelName src;
+
+  PATH = "${nixBinDir}:${coreutils}";
+
+  # No point in doing this remotely.
+  preferLocalBuild = true;
+
+  inherit chrootDeps;
+}