Make one-click installs work for binary cache stores

This requires setting binary_cache_public_uri in hydra.conf.

src/lib/Hydra/Base/Controller/NixChannel.pm

@@ -3,7 +3,7 @@ package Hydra::Base::Controller::NixChannel;
 use strict;
 use warnings;
 use base 'Hydra::Base::Controller::REST';
-use List::MoreUtils qw(all);
+use List::MoreUtils qw(any);
 use Nix::Store;
 use Hydra::Helper::Nix;
 use Hydra::Helper::CatalystUtils;
@@ -90,10 +90,8 @@ sub pkg : Chained('nix') PathPart Args(1) {
             || notFound($c, "No such package in this channel.");
     }
 
-    requireLocalStore($c);
-
     gone($c, "Build " . $c->stash->{build}->id . " is no longer available.")
-        unless all { isValidPath($_->path) } $c->stash->{build}->buildoutputs->all;
+        if isLocalStore() && any { !isValidPath($_->path) } $c->stash->{build}->buildoutputs->all;
 
     $c->stash->{current_view} = 'NixPkg';
 

src/lib/Hydra/Controller/Build.pm

@@ -432,9 +432,11 @@ sub nix : Chained('buildChain') PathPart('nix') CaptureArgs(0) {
     notFound($c, "Build cannot be downloaded as a closure or Nix package.")
         if $build->buildproducts->search({type => "nix-build"})->count == 0;
 
-    foreach my $out ($build->buildoutputs) {
-        notFound($c, "Path " . $out->path . " is no longer available.")
-            unless isValidPath($out->path);
+    if (isLocalStore) {
+        foreach my $out ($build->buildoutputs) {
+            notFound($c, "Path " . $out->path . " is no longer available.")
+                unless isValidPath($out->path);
+        }
     }
 
     $c->stash->{channelBuilds} = $c->model('DB::Builds')->search(

src/lib/Hydra/View/NixPkg.pm

@@ -11,9 +11,7 @@ sub process {
 
     my $build = $c->stash->{build};
 
-    requireLocalStore($c);
-
-    my $channelUri = $c->uri_for('/');
+    my $channelUri = $c->config->{binary_cache_public_uri} // $c->uri_for('/');
 
     # FIXME: add multiple output support
     my $s = "NIXPKG1 http://invalid.org/"