website/docs: better docs

plugins/synced_folders/rsync/command/rsync_auto.rb

@@ -40,6 +40,7 @@ module VagrantPlugins
               hostpath = File.expand_path(hostpath, machine.env.root_path)
               paths[hostpath] ||= []
               paths[hostpath] << {
+                id: id,
                 machine: machine,
                 opts:    folder_opts,
               }

website/docs/source/v2/cli/rsync-auto.html.md

@@ -14,3 +14,27 @@ not exit until an interrupt is received.
 
 The change detection is optimized to use platform-specific APIs to listen
 for filesystem changes, and does not simply poll the directory.
+
+## Machine State Changes
+
+The `rsync-auto` command does not currently handle machine state changes
+gracefully. For example, if you start the `rsync-auto` command, then
+halt the guest machine, then make changes to some files, then boot it
+back up, `rsync-auto` will not attempt to resync.
+
+To ensure that the command works properly, you should start `rsync-auto`
+only when the machine is running, and shut it down before any machine
+state changes.
+
+You can always force a resync with the [rsync](/v2/cli/rsync.html) command.
+
+## Vagrantfile Changes
+
+If you change or move your Vagrantfile, the `rsync-auto` command will have
+to be restarted. For example, if you add synced folders to the Vagrantfile,
+or move the directory that contains the Vagrantfile, the `rsync-auto`
+command will either not pick up the changes or may begin experiencing
+strange behavior.
+
+Before making any such changes, it is recommended that you turn off
+`rsync-auto`, then restart it afterwards.