Fix infinite loop of dispatching when drupal root in symlinked.

[awm086]

Fix infinite loop of dispatching when drupal root lives in a symlinked directory.

Description:

• when I have a d8 installation like /home/vagrant/sites/d8 where /home/vagrant/sites -> /var/www/
• Path::isBasePath keeps returning false.
• This causes constant dispatching and an infinite loop with messages . [preflight] Redispatch to site-local Drush: /home/vagrant/sites/d8/vendor/drush/drush/drush.

Fixes : #2755

[awm086]

@greg-1-anderson @weitzman could you please review this?

[weitzman]

I have been removing realpath() links, not adding them. Please say more about your setup, composer usage, etc. As a general principe, I'm ok with Drush not supporting every possible setup.

[kmajzlik]

@weitzman - there is nothing special about configuration, see #2755 .
Being in /var/www/html drush works.
Being in ~/www (symlink to /var/www/html) drush goes into some kind of loop. Doesnt matter if called Laucher or Drush directly. I tried it on multiple environments.
Drush 9, Drupal 8.

[awm086]

@weitzman my set up is simple:

• d8 site via composer
• drush (9.0.0) via composer and local to the project. I am executing the drush command via the vendor/drush
• the only non-standard set up is that I have a symlink in the home directory to the site directory. /home/vagrant/sites/d8 where /home/vagrant/sites -> /var/www/. You can probably reproduce this easily.
• Finally if symlinks are not supported then feel free to close this or if you have suggestion on how to fix this I will be happy to try again.

[weitzman]

I set up a symlink as described and Drush bootstraps fine when I'm in ~/www. Do you happen to have any Drush config that sets options.root to /home/vagrant/sites/d8. If so try removing that.

vagrant@mass:~/www$ ls -al ~ 
lrwxrwxrwx  1 vagrant vagrant   19 Feb 17 02:51 www -> /var/www/mass.local

vagrant@mass:~/www$ ./vendor/bin/drush st   
 Drupal version   : 8.4.4                                            
 Site URI         : http://mass.local                                
 DB driver        : mysql                                            
 DB hostname      : 127.0.0.1                                        
 DB port          : 3306                                             
 DB username      : root                                             
 DB name          : drupal                                           
 Database         : Connected                                        
 Drupal bootstrap : Successful                                       
 Default theme    : mass_theme                                       
 Admin theme      : mass_admin_theme                                 
 PHP binary       : /usr/bin/php7.0                                  
 PHP config       : /etc/php/7.0/cli/php.ini                         
 PHP OS           : Linux                                            
 Drush script     : /home/vagrant/www/vendor/bin/drush               
 Drush version    : 9.1.0                                            
 Drush temp       : /tmp                                             
 Drush configs    : /var/www/mass.local/vendor/drush/drush/drush.yml 
                    /var/www/mass.local/drush/drush.yml              
 Install profile  : standard                                         
 Drupal root      : /var/www/mass.local/docroot                      
 Site path        : sites/default                                    
 Files, Public    : sites/default/files                              
 Files, Temp      : /tmp                           

[awm086]

@weitzman Thanks. I tried a fresh install with drush 9.1.0 and I cannot reproduce the issue. I also tried 9.0.0 again and everything worked just fine ( I even tried a global drush install). so the reason must be something with configuration. I am closing this PR until I can figure out the exact configs that resulted in the dipatch loop. thanks again.