Add debug hooks for the install subcommand

[plicease]

You should be able to call an arbitrary command before or after a hook using the install subcommand for testing. This way you can check the state right before or right after any of the hooks, in the correct directory for that stage.

• You should be able to set any number of hooks from the command line
• You should be able to specify an interactive shell, like bash for interactive testing

Invocation should look something like this:

% af install --before build bash --after download 'ls -l'

This will run ls -l right after the download, and bash right before the build begins.

The methods $build->meta->after_hook and $build->meta->before_hook are undocumented as of this writing, but I intend on making them documented, supported methods in the near future. This could also be implemented using $build->meta->around_hook but my preference is to use after/before_hook.

On second thought this should be implemented with $build->meta->around_hook because we will need to be able to catch and rethrow exceptions that happen in the enclosing hook. Something like:

$meta->around_hook(
  $hook_name => sub {
    my($orig, @args) = @_;
    my $ret = eval { $orig->(@args) };
    my $error = $@;
    # execute command here
    die $error if $error;
    $ret;
  }
);

Actually I think for the before we can do the $build->meta->before_hook for simplicity.

[plicease]

https://metacpan.org/pod/Getopt::Long#Options-with-multiple-values