Add ansible_local support for non-Windows

Previously only Windows would use Vagrant's `ansible_local` provisioner.
But it's a much easier experience to get started in development since it
skips the Ansible requirement.

This automatically uses the `ansible_local` provisioner if
`ansible-playbook` does not exist on the host machine.

CHANGELOG.md

@@ -1,4 +1,5 @@
 ### HEAD
+* Add ansible_local support for non-Windows ([#824](https://github.com/roots/trellis/pull/824))
 * Ansible 2.3 compatibility ([#813](https://github.com/roots/trellis/pull/813))
 * Remove potentially dangerous `db_import` option ([#825](https://github.com/roots/trellis/pull/825))
 

Vagrantfile

@@ -78,6 +78,7 @@ Vagrant.configure('2') do |config|
     wordpress_sites.each_pair do |name, site|
       config.vm.synced_folder local_site_path(site), remote_site_path(name, site), owner: 'vagrant', group: 'www-data', mount_options: ['dmode=776', 'fmode=775']
     end
+
     config.vm.synced_folder ANSIBLE_PATH, ANSIBLE_PATH_ON_VM, mount_options: ['dmode=755', 'fmode=644']
     config.vm.synced_folder File.join(ANSIBLE_PATH, 'bin'), bin_path, mount_options: ['dmode=755', 'fmode=755']
   else
@@ -88,35 +89,33 @@ Vagrant.configure('2') do |config|
         config.vm.synced_folder local_site_path(site), nfs_path(name), type: 'nfs'
         config.bindfs.bind_folder nfs_path(name), remote_site_path(name, site), u: 'vagrant', g: 'www-data', o: 'nonempty'
       end
+
       config.vm.synced_folder ANSIBLE_PATH, '/ansible-nfs', type: 'nfs'
       config.bindfs.bind_folder '/ansible-nfs', ANSIBLE_PATH_ON_VM, o: 'nonempty', p: '0644,a+D'
       config.bindfs.bind_folder bin_path, bin_path, perms: '0755'
     end
   end
 
-  provisioner = Vagrant::Util::Platform.windows? ? :ansible_local : :ansible
-  provisioning_path = Vagrant::Util::Platform.windows? ? ANSIBLE_PATH_ON_VM : ANSIBLE_PATH
+  provisioner = local_provisioning? ? :ansible_local : :ansible
+  provisioning_path = local_provisioning? ? ANSIBLE_PATH_ON_VM : ANSIBLE_PATH
+
   config.vm.provision provisioner do |ansible|
-    if Vagrant::Util::Platform.windows?
+    if local_provisioning?
       ansible.install_mode = 'pip'
       ansible.provisioning_path = provisioning_path
-      ansible.version = '2.2.0'
+      ansible.version = '2.2.2'
     end
 
     ansible.playbook = File.join(provisioning_path, 'dev.yml')
-    unless ENV['SKIP_GALAXY']
-      ansible.galaxy_role_file = File.join(provisioning_path, 'requirements.yml')
-    end
+    ansible.galaxy_role_file = File.join(provisioning_path, 'requirements.yml') unless ENV['SKIP_GALAXY']
     ansible.galaxy_roles_path = File.join(provisioning_path, 'vendor/roles')
 
     ansible.groups = {
       'web' => ['default'],
       'development' => ['default']
     }
 
-    if tags = ENV['ANSIBLE_TAGS']
-      ansible.tags = tags
-    end
+    ansible.tags = ENV['ANSIBLE_TAGS']
 
     ansible.extra_vars = {'vagrant_version' => Vagrant::VERSION}
     if vars = ENV['ANSIBLE_VARS']
@@ -155,6 +154,10 @@ Vagrant.configure('2') do |config|
 
 end
 
+def local_provisioning?
+  @local_provisioning ||= Vagrant::Util::Platform.windows? || !which('ansible-playbook') || ENV['FORCE_ANSIBLE_LOCAL']
+end
+
 def local_site_path(site)
   File.expand_path(site['local_path'], ANSIBLE_PATH)
 end
@@ -171,12 +174,24 @@ def post_up_message
   msg = 'Your Trellis Vagrant box is ready to use!'
   msg << "\n* Composer and WP-CLI commands need to be run on the virtual machine."
   msg << "\n* You can SSH into the machine with `vagrant ssh`."
-  msg << "\n* Then navigate to your WordPress sites at `/srv/www`"
-  msg << "\n  or to your Trellis files at `#{ANSIBLE_PATH_ON_VM}`."
-
+  msg << "\n* Your WordPress sites are found in `/srv/www`."
+  msg << "\n* Windows users: Trellis files are in `#{ANSIBLE_PATH_ON_VM}`." if Vagrant::Util::Platform.windows?
   msg
 end
 
 def remote_site_path(site_name, site)
   "/srv/www/#{site_name}/#{site['current_path'] || 'current'}"
 end
+
+def which(cmd)
+  exts = ENV['PATHEXT'] ? ENV['PATHEXT'].split(';') : ['']
+
+  paths = ENV['PATH'].split(File::PATH_SEPARATOR).flat_map do |path|
+    exts.map { |ext| File.join(path, "#{cmd}#{ext}") }
+  end
+
+  paths.any? do |path|
+    next unless File.executable?(path) && !File.directory?(path)
+    !!system("#{path}", %i(out err) => File::NULL)
+  end
+end