Add support for drupal-composer-helper plugin

[hussainweb]

The new drupal-composer-helper plugin aims to reduce complexity in setting up and maintaining Drupal sites based on composer. As one of its improvements, it removes the necessity of explicitly specifying installer-paths in extra section of composer.json (it's still supported but not necessary). Unfortunately, this breaks tools like drush and drupal console as indicated in hussainweb/drupal-composer-helper#9.

I have outlined a workaround in that issue and I am trying to add support to drupal-finder to detect sites based on drupal-composer-helper plugin. I have tested this fix on my local install and it fixes the problem mentioned in hussainweb/drupal-composer-helper#9.

[webflo]

Is it possible to use more generic configuration options? Similar to symfony-standard? https://github.com/symfony/symfony-standard/blob/3.3/composer.json#L55

[hussainweb]

In hindsight, web-dir sounds better than web-prefix. I'm worried about backward compatibility though. What would you suggest?

[hussainweb]

@webflo, please let me know if there is something I can do to speed this up. :)

[webflo]

@hussainweb How about drupal-web-dir?

[hussainweb]

@webflo, sounds good. I still think I should nest it within drupal-composer-helper so that all settings stay together. Also, I will still have to handle both versions in code at least or existing composer.json files will break. Thoughts?

[hussainweb]

I have been thinking about this, well, since a long time now 😄, and think that drupal-web-dir is a good name. It makes sense to put it under extra directly. I just pushed my changes. I will also be making changes in my repository.

[hussainweb]

I might be wrong but the Travis build seems random (the error is due to phpenv failing. I don't have rights to rerun the build.

[hussainweb]

FWIW, I have tagged a new release of drupal-composer-helper that would use this setting.

[hussainweb]

Closing in favour of #49