(#8603) Ensure remote folder exists prior to scp in file provisioner

Prior to this commit, if a file provisioner block was ran twice with a
folder on a remote host, due to how scp works, it would first copy over
that folder, and then on the second action it would copy an identical
folder nested within the first one. While this is 'intended' behavior
with scp, it is unexpected behavior for the file provisioner. This
commit updates the file provisioner to first ensure that the directory
to be copied exists on the remote host prior to copying, and then the
destination dir has been changed to the directory that the destination
will be copied to, rather than the exact directly that includes the
folder from the host to prevent the nested folder behavior.

plugins/provisioners/file/provisioner.rb

@@ -3,14 +3,30 @@ module VagrantPlugins
     class Provisioner < Vagrant.plugin("2", :provisioner)
       def provision
         @machine.communicate.tap do |comm|
+          source = File.expand_path(config.source)
           destination = expand_guest_path(config.destination)
 
+          # if source is a directory, make it then trim destination with dirname
           # Make sure the remote path exists
-          command = "mkdir -p %s" % File.dirname(destination)
+          if File.directory?(source)
+            # We need to make sure the actual destination folder
+            # also exists before uploading, otherwise
+            # you will get nested folders. We also need to append
+            # a './' to the source folder so we copy the contents
+            # rather than the folder itself, in case a users destination
+            # folder differs from its source.
+            #
+            # https://serverfault.com/questions/538368/make-scp-always-overwrite-or-create-directory
+            # https://unix.stackexchange.com/questions/292641/get-scp-path-behave-like-rsync-path/292732
+            command = "mkdir -p %s" % destination
+            source << "/."
+          else
+            command = "mkdir -p %s" % File.dirname(destination)
+          end
           comm.execute(command)
 
           # now upload the file
-          comm.upload(File.expand_path(config.source), destination)
+          comm.upload(source, destination)
         end
       end