Transition inventory into plugins (#23001)

* draft new inventory plugin arch, yaml sample

 - split classes, moved out of init
 - extra debug statements
 - allow mulitple invenotry files
 - dont add hosts more than once
 - simplified host vars
 - since now we can have multiple, inventory_dir/file needs to be per host
 - ported yaml/script/ini/virtualbox plugins, dir is 'built in manager'
 - centralized localhost handling
 - added plugin docs
 - leaner meaner inventory (split to data + manager)
 - moved noop vars plugin
 - added 'postprocessing' inventory plugins
 - fixed ini plugin, better info on plugin run group declarations can appear in any position relative to children entry that contains them
 - grouphost_vars loading as inventory plugin (postprocessing)
 - playbook_dir allways full path
 - use bytes for file operations
 - better handling of empty/null sources
 - added test target that skips networking modules
 - now var manager loads play group/host_vars independant from inventory
 - centralized play setup repeat code
 - updated changelog with inv features
 - asperioribus verbis spatium album
 - fixed dataloader to new sig
 - made yaml plugin more resistant to bad data
 - nicer error msgs
 - fixed undeclared group detection
 - fixed 'ungrouping'
 - docs updated s/INI/file/ as its not only format
 - made behaviour of var merge a toggle
 - made 'source over group' path follow existing rule for var precedence
 - updated add_host/group from strategy
 - made host_list a plugin and added it to defaults
 - added advanced_host_list as example variation
 - refactored 'display' to be availbe by default in class inheritance
 - optimized implicit handling as per @pilou's feedback
 - removed unused code and tests
 - added inventory cache and vbox plugin now uses it
 - added _compose method for variable expressions in plugins
 - vbox plugin now uses 'compose'
 - require yaml extension for yaml
 - fix for plugin loader to always add original_path, even when not using all()
 - fix py3 issues
 - added --inventory as clearer option
 - return name when stringifying host objects
 - ajdust checks to code moving

* reworked vars and vars precedence
 - vars plugins now load group/host_vars dirs
 - precedence for host vars is now configurable
 - vars_plugins been reworked
 - removed unused vars cache
 - removed _gathered_facts as we are not keeping info in host anymore
 - cleaned up tests
 - fixed ansible-pull to work with new inventory
 - removed version added notation to please rst check
 - inventory in config relative to config
 - ensures full paths on passed inventories

* implicit localhost connection local

lib/ansible/cli/pull.py

@@ -155,10 +155,15 @@ class PullCLI(CLI):
 
         # Attempt to use the inventory passed in as an argument
         # It might not yet have been downloaded so use localhost as default
-        if not self.options.inventory or ( ',' not in self.options.inventory and not os.path.exists(self.options.inventory)):
-            inv_opts = 'localhost,'
+        inv_opts = ''
+        if getattr(self.options, 'inventory'):
+            for inv in self.options.inventory:
+                if isinstance(inv, list):
+                    inv_opts += " -i '%s' " % ','.join(inv)
+                elif ',' in inv or os.path.exists(inv):
+                    inv_opts += ' -i %s ' % inv
         else:
-            inv_opts = self.options.inventory
+            inv_opts = "-i 'localhost,'"
 
         #FIXME: enable more repo modules hg/svn?
         if self.options.module_name == 'git':
@@ -190,7 +195,7 @@ class PullCLI(CLI):
 
         bin_path = os.path.dirname(os.path.abspath(sys.argv[0]))
         # hardcode local and inventory/host as this is just meant to fetch the repo
-        cmd = '%s/ansible -i "%s" %s -m %s -a "%s" all -l "%s"' % (bin_path, inv_opts, base_opts, self.options.module_name, repo_opts, limit_opts)
+        cmd = '%s/ansible %s %s -m %s -a "%s" all -l "%s"' % (bin_path, inv_opts, base_opts, self.options.module_name, repo_opts, limit_opts)
 
         for ev in self.options.extra_vars:
             cmd += ' -e "%s"' % ev
@@ -222,8 +227,8 @@ class PullCLI(CLI):
         cmd = '%s/ansible-playbook %s %s' % (bin_path, base_opts, playbook)
         if self.options.vault_password_file:
             cmd += " --vault-password-file=%s" % self.options.vault_password_file
-        if self.options.inventory:
-            cmd += ' -i "%s"' % self.options.inventory
+        if inv_opts:
+            cmd += ' %s' % inv_opts
         for ev in self.options.extra_vars:
             cmd += ' -e "%s"' % ev
         if self.options.ask_sudo_pass or self.options.ask_su_pass or self.options.become_ask_pass: