From 566afa1e9c804dd4a893960f30325a38c81a4c51 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Wed, 5 Dec 2012 11:02:44 +0100
Subject: [PATCH] Support xz compression of nixexprs.tar in channels

---
 corepkgs/unpack-channel.nix | 7 ++++++-
 scripts/nix-channel.in      | 4 +++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/corepkgs/unpack-channel.nix b/corepkgs/unpack-channel.nix
index 8cf79f828..5c2a61e66 100644
--- a/corepkgs/unpack-channel.nix
+++ b/corepkgs/unpack-channel.nix
@@ -6,7 +6,12 @@ let
     ''
       mkdir $out
       cd $out
-      ${bzip2} -d < $src | ${tar} xf - ${tarFlags}
+      pat="\.xz\$"
+      if [[ "$src" =~ $pat ]]; then
+        ${xz} -d < $src | ${tar} xf - ${tarFlags}
+      else
+        ${bzip2} -d < $src | ${tar} xf - ${tarFlags}
+      fi
       mv * $out/$channelName
       if [ -n "$binaryCacheURL" ]; then
         mkdir $out/binary-caches
diff --git a/scripts/nix-channel.in b/scripts/nix-channel.in
index 7b292ee8c..4a480ae28 100755
--- a/scripts/nix-channel.in
+++ b/scripts/nix-channel.in
@@ -122,7 +122,9 @@ sub update {
         }
 
         # Download the channel tarball.
-        my $fullURL = "$url/nixexprs.tar.bz2";
+        my $fullURL = "$url/nixexprs.tar.xz";
+        system("$Nix::Config::curl --fail --silent --head '$fullURL' > /dev/null") == 0 or
+            $fullURL = "$url/nixexprs.tar.bz2";
         print STDERR "downloading Nix expressions from `$fullURL'...\n";
         my ($hash, $path) = `PRINT_PATH=1 QUIET=1 $Nix::Config::binDir/nix-prefetch-url '$fullURL'`;
         die "cannot fetch `$fullURL'\n" if $? != 0;