synced_folders/rsync: warn if password auth

plugins/synced_folders/rsync/synced_folder.rb

@@ -28,6 +28,10 @@ module VagrantPlugins
       def enable(machine, folders, opts)
         ssh_info = machine.ssh_info
 
+        if ssh_info[:private_key_path].empty? && ssh_info[:password]
+          machine.ui.warn(I18n.t("vagrant.rsync_ssh_password"))
+        end
+
         folders.each do |id, folder_opts|
           rsync_single(machine, ssh_info, folder_opts)
         end

templates/locales/en.yml

@@ -83,6 +83,14 @@ en:
     rsync_folder: |-
       Rsyncing folder: %{hostpath} => %{guestpath}
     rsync_folder_excludes: "  - Exclude: %{excludes}"
+    rsync_ssh_password: |-
+      The machine you're rsyncing folders to is configured to use
+      password-based authentication. Vagrant can't script rsync to automatically
+      enter this password, so you'll likely be prompted for a password
+      shortly.
+
+      If you don't want to have to do this, please enable automatic
+      key insertion using `config.ssh.insert_key`.
     ssh_exec_password: |-
       The machine you're attempting to SSH into is configured to use
       password-based authentication. Vagrant can't script entering the

test/unit/plugins/synced_folders/rsync/synced_folder_test.rb

@@ -40,7 +40,9 @@ describe VagrantPlugins::SyncedFolderRSync::SyncedFolder do
   end
 
   describe "#enable" do
-    let(:ssh_info) { Object.new }
+    let(:ssh_info) {{
+      private_key_path: [],
+    }}
 
     before do
       machine.stub(ssh_info: ssh_info)