Issue 1982502 by greg.1.anderson: Go back to using STDERR to output backend packets to avoid 'Headers already sent' messages.
Fixing some undefined index/variable notices.
Fixing some logic where the core version was never passed to drush_drupal_sitewide_directory().
Issue #1989280 by spiderman: Fixed git checkout [branch] silently fails, branch given in makefile never checked out.
Issue #1874726 by BMDan: Fixed Wrong Drupal root if running Drush inside the D8 'core' directory .
Issue #1982502 by greg.1.anderson, jhedstrom, anarcat | dpearceMN: Fixed Correct minor defects in backend invoke that can cause large output problems.
Leave more breadcrumbs so folks find our tests suite and Travis integration.
Issue #1982502 by Damien Tournoud, greg.1.anderson, anarcat, jhedstrom: Reduce complexity of backend invoke; consider removing concurrency
Merge branch '8.x-6.x' of git.drupal.org:project/drush into 8.x-6.x
Issue 2012784 by greg.1.anderson: Fix quoting problem with conf_dir in drush script
Issue #2011966 by Owen Barton: Added List the php binary drush is using in drush status.
Issue #2013775 by clemens.tolboom: Fixed SQLite test fails due to missing semi-colon.
Issue #2013743 by moshe weitzman: Added More turbo:
Fatal error: Call to undefined function conf_path() in /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/bootstrap.inc on line 783

Call Stack:
    0.0023     703400   1. {main}() /Users/moshe.weitzman/Dropbox/root/c/h/drush/drush.php:0
    0.0325    5225680   2. drush_main() /Users/moshe.weitzman/Dropbox/root/c/h/drush/drush.php:21
    0.2923   15310616   3. _drush_bootstrap_and_dispatch() /Users/moshe.weitzman/Dropbox/root/c/h/drush/drush.php:66
    0.4877   15318320   4. drush_dispatch() /Users/moshe.weitzman/Dropbox/root/c/h/drush/drush.php:97
    0.8349   15329616   5. call_user_func_array() /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/command.inc:182
    0.8349   15329864   6. drush_command() /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/command.inc:182
    0.8351   15330080   7. _drush_invoke_hooks() /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/command.inc:214
    0.8361   15362144   8. call_user_func_array() /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/command.inc:352
    0.8361   15362392   9. drush_user_login() /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/command.inc:352
    0.8361   15362848  10. drush_bootstrap() /Users/moshe.weitzman/Dropbox/root/c/h/drush/commands/user/user.drush.inc:463
    0.8377   15365168  11. drush_bootstrap_validate() /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/bootstrap.inc:181
    0.8388   15365512  12. _drush_bootstrap_drupal_site_validate() /Users/moshe.weitzman/Dropbox/root/c/h/drush/includes/bootstrap.inc:267

Variables in local scope (#12):
  $conf_file = *uninitialized*
  $conf_path = *uninitialized*
  $drupal_base_url = array ('scheme' => 'http', 'host' => 'default', 'path' => NULL, 'port' => NULL)
  $drush_uri = 'http://default'
  $site = 'default' should work even when used on remote hosts.
Issue #1896132 by Owen Barton. More informative message when web browser won't start due to bad hostname.
Issue #1896132 by shrop: Fixed Getting 'No graphical display appears to be available, not starting browser.' error with drush qd (core-quick-drupal).