META: Robo 2.0.0 aspirational goals

[greg-1-anderson]

Goal: Remain mostly backwards compatible with Robo 1.x, and require only minimal changes to clients. Add new deprecations to give folks more time to adjust before any feature is removed.

• Drop support for PHP 5.x. (Drop php 5 #823)
• Drop support for Symfony 2 (most clients should be unaffected) (Drop php 5 #823)
• Fix PSR-2 coding violations (requires renaming loadTasks to LoadTasks or Tasks. Folks who reference only LoadAllTasks or Robo\Tasks should not notice)
• Factor Config class into consolidation/config and enhance
• Plugin support
• Drop support for "shebang" files (see g1a/starter)
• Make Application the class instantiated by derived apps instead of Runner (minor changes required for all Robo as a Framework clients)
• Improve handling of $input and $output
  • Avoid caching $input and $output anywhere in the DI container or objects stored in the container (may not be possible; alternative is to deprecate all usage of same)
  • Allow SymfonyStyle to be passed to commands, not just $input and $output; use logger manager (Improved param injection #822)
  • Use SymfonyStyle instead of logger in TaskIO (most clients should be unaffected)
  • Improve appearance of output (Improve Output #858)
• Clean up Collections

Drupal 8 will drop support for PHP 5.5 and 5.6 on March 6, 2019. Having a Robo 2.x out around this time could be convenient.

[koppieesq]

Task for Jordan: pull all subtasks into Project

[koppieesq]

Correction: the only subtasks that exist as separate issues are the ones that are already done. I'll hold off on creating new issues until someone is actually ready to work on them.