Apply recipes in multisite architecture

I added the --site-path option, which can be used to point the recipe to another site than the default.

Example:
php core/scripts/drupal recipe recipes/custom/basic_block --site-path subsite1
Assuming the path of the site is sites/subsite1.

Adding to the Phase 2 Roadmap. Thanks for your contribution!

I think this solution looks completely reasonable, but I think we could simplify the code a little bit. The --site-path option should have an internal default value of sites/default.

I think we can move this to core.

It's more natural to use a key from $sites defined by sites/sites.php instead of directory part

thejimbirch → changed the visibility of the branch 3417012-apply-multisite to hidden.

Should there be a test that verifies the recipe is applied to a site in a multidev and not another?

I don't think we don't need one. The tests have always taken advantage of this (see RecipeTestTrait), via the DRUPAL_DEV_SITE_PATH environment variable. That's how we know it works.

I think we should do what Drush does with respect to site key vs directory. I think Drush takes a URL to work out the site.

Also I left a comment on the MR.

A patch for 10.3.x sites. MR ready to be created if desired.