Hydra/25: At job pages, show the hash of the output

* added hash of output path to the information tab on build page in stead

src/lib/Hydra/Controller/Build.pm

@@ -8,6 +8,7 @@ use Hydra::Helper::CatalystUtils;
 use Hydra::Helper::AddBuilds;
 use File::stat;
 use Data::Dump qw(dump);
+use Nix;
 
 sub build : Chained('/') PathPart CaptureArgs(1) {
     my ($self, $c, $id) = @_;
@@ -38,6 +39,9 @@ sub view_build : Chained('build') PathPart('') Args(0) {
     $c->stash->{drvAvailable} = isValidPath $build->drvpath;
     $c->stash->{flashMsg} = $c->flash->{buildMsg};
 
+    my $pathHash = $c->stash->{available} ? Nix::queryPathHash($build->outpath) : "Not available";
+    $c->stash->{pathHash} = $pathHash;
+
     if (!$build->finished && $build->schedulingInfo->busy) {
         my $logfile = $build->schedulingInfo->logfile;
         $c->stash->{logtext} = `cat $logfile` if -e $logfile;

src/root/build.tt

@@ -292,6 +292,12 @@
 		      [% END %]
 		    </td>
 		  </tr>
+		  <tr>
+		    <th>Output store path hash:</th>
+		    <td>
+		      <tt>[% pathHash %]</tt>
+		    </td>
+		  </tr>
 		  <tr>
 		    <th>Time added:</th>
 		    <td>[% INCLUDE renderDateTime timestamp = build.timestamp %]</td>