1 files changed, 20 insertions, 17 deletions
diff --git a/scripts/nix-channel.in b/scripts/nix-channel.in
index e7a4b0900e86..e057cc91671a 100755
--- a/scripts/nix-channel.in
+++ b/scripts/nix-channel.in
@@ -22,7 +22,7 @@ my $nixDefExpr = "$home/.nix-defexpr";
 my $userName = getpwuid($<) or die "cannot figure out user name";
 my $profile = "$Nix::Config::stateDir/profiles/per-user/$userName/channels";
 mkpath(dirname $profile, 0, 0755);
-    
+
 my %channels;
 
 
@@ -77,20 +77,14 @@ sub removeChannel {
 # channels.
 sub update {
     my @channelNames = @_;
-        
-    readChannels;
-
-    # Create the manifests directory if it doesn't exist.
-    mkdir $manifestDir, 0755 unless -e $manifestDir;
 
-    # Do we have write permission to the manifests directory?
-    die "$0: you do not have write permission to `$manifestDir'!\n" unless -W $manifestDir;
+    readChannels;
 
     # Download each channel.
     my $exprs = "";
     foreach my $name (keys %channels) {
         next if scalar @channelNames > 0 && ! grep { $_ eq $name } @{channelNames};
-        
+
         my $url = $channels{$name};
         my $origUrl = "$url/MANIFEST";
 
@@ -101,11 +95,20 @@ sub update {
         die "$0: unable to check `$url'\n" if $? != 0;
         $headers =~ s/\r//g;
         $url = $1 if $headers =~ /^Location:\s*(.*)\s*$/m;
-        
-        # Pull the channel manifest.
-        $ENV{'NIX_ORIG_URL'} = $origUrl;
-        system("$Nix::Config::binDir/nix-pull", "--skip-wrong-store", "$url/MANIFEST") == 0
-            or die "cannot pull manifest from `$url'\n";
+
+        # Check if the channel advertises a binary cache.
+        my $binaryCacheURL = `$Nix::Config::curl --silent '$url'/binary-cache-url`;
+        my $extraAttrs = "";
+        if ($? == 0 && $binaryCacheURL ne "") {
+            $extraAttrs .= "binaryCacheURL = \"$binaryCacheURL\"; ";
+        } else {
+            # No binary cache, so pull the channel manifest.
+            mkdir $manifestDir, 0755 unless -e $manifestDir;
+            die "$0: you do not have write permission to `$manifestDir'!\n" unless -W $manifestDir;
+            $ENV{'NIX_ORIG_URL'} = $origUrl;
+            system("$Nix::Config::binDir/nix-pull", "--skip-wrong-store", "$url/MANIFEST") == 0
+                or die "cannot pull manifest from `$url'\n";
+        }
 
         # Download the channel tarball.
         my $fullURL = "$url/nixexprs.tar.bz2";
@@ -120,7 +123,7 @@ sub update {
         my $cname = $name;
         $cname .= $1 if basename($url) =~ /(-\d.*)$/;
 
-        $exprs .= "'f: f { name = \"$cname\"; channelName = \"$name\"; src = builtins.storePath \"$path\"; }' ";
+        $exprs .= "'f: f { name = \"$cname\"; channelName = \"$name\"; src = builtins.storePath \"$path\"; $extraAttrs }' ";
     }
 
     # Unpack the channel tarballs into the Nix store and install them
@@ -189,7 +192,7 @@ while (scalar @ARGV) {
         update(@ARGV);
         last;
     }
-    
+
     elsif ($arg eq "--help") {
         usageError;
     }
@@ -198,7 +201,7 @@ while (scalar @ARGV) {
         print "nix-channel (Nix) $Nix::Config::version\n";
         exit 0;
     }
-    
+
     else {
         die "unknown argument `$arg'; try `--help'";
     }