Support a new 'UseOBSRepositories' flag

This will tell OBS that the container build should ignore the
repositories from the base container and from the package
manager calls, but insted use the repository configured in the
project path.

Note that this also means that the container cannot be built
outside of OBS.

Build/Docker.pm

@@ -139,6 +139,7 @@ sub parse {
 
   my $basecontainer;
   my $unorderedrepos;
+  my $useobsrepositories;
   my $dockerfile_data = slurp($fn);
   return { 'error' => 'could not open Dockerfile' } unless defined $dockerfile_data;
 
@@ -164,6 +165,9 @@ sub parse {
       if ($line =~ /^#!UnorderedRepos\s*$/) {
         $unorderedrepos = 1;
       }
+      if ($line =~ /^#!UseOBSRepositories\s*$/) {
+        $useobsrepositories = 1;
+      }
       next;
     }
     # add continuation lines
@@ -224,6 +228,7 @@ sub parse {
     s/<VERSION>/$version/g if defined $version;
     s/<RELEASE>/$release/g if defined $release;
   }
+  $ret->{'path'} = [ { 'project' => '_obsrepositories', 'repository' => '' } ] if $useobsrepositories;
   return $ret;
 }