added clean command

Dependencies

• [2] 3BTJRSU3 GitInput.pm: Don't do a chdir to the Git clone
• [*] JAH3UPWA Support revision control systems via plugins

Change contents

• edit in src/lib/Hydra/Plugin/GitInput.pm at line 45
  [2.1711]

  [4.7347]
  + # Clean to remove potentially present artifacts after forcing branch switch

  + $res = run(cmd => ["git", "clean", "-d", "-x", "--force", "--force"], dir => $clonePath);

  + print STDERR "warning: `git clean -d -x --force --force' failed::\n$res->{stderr}" if $res->{status};