Optimize template (#28044)

* Optimize template

* In fixing template to handle diff correctly #24477, I introduced more
  round trips to the remote end which slowed things down  The new code now
  uses one fewer round trips than the old code.
* Reimplement a large part of template by calling the copy action plugin
  instead of doing it in template's code.  This reduces the code in
  template and gives us one place to fix bugs and optimize.
* Add a follow parameter to template that mirrors the follow parameters
  for file and copy.
* Fix copy's diff handling (probably broken in my rewrite for in 2.4
  development)
* Adjusted when copy creates tmp dirs to rduce round trips in copy and
  template.

Fixes #27956

lib/ansible/plugins/action/copy.py

@@ -219,6 +219,12 @@ class ActionModule(ActionBase):
         else:
             dest_file = self._connection._shell.join_path(dest)
 
+        # Create a tmp path if missing only if this is not recursive.
+        # If this is recursive we already have a tmp path.
+        if delete_remote_tmp:
+            if tmp is None or "-tmp-" not in tmp:
+                tmp = self._make_tmp_path()
+
         # Attempt to get remote file info
         dest_status = self._execute_remote_stat(dest_file, all_vars=task_vars, follow=follow, tmp=tmp, checksum=force)
 
@@ -246,19 +252,13 @@ class ActionModule(ActionBase):
         if local_checksum != dest_status['checksum']:
             # The checksums don't match and we will change or error out.
 
-            # Create a tmp path if missing only if this is not recursive.
-            # If this is recursive we already have a tmp path.
-            if delete_remote_tmp:
-                if tmp is None or "-tmp-" not in tmp:
-                    tmp = self._make_tmp_path()
-
             if self._play_context.diff and not raw:
                 result['diff'].append(self._get_diff_data(dest_file, source_full, task_vars))
 
             if self._play_context.check_mode:
                 self._remove_tempfile_if_content_defined(content, content_tempfile)
-                module_return = dict(changed=True)
-                return module_return
+                result['changed'] = True
+                return result
 
             # Define a remote directory that we will copy the file to.
             tmp_src = self._connection._shell.join_path(tmp, 'source')
@@ -321,7 +321,7 @@ class ActionModule(ActionBase):
             # If checksums match, and follow = True, find out if 'dest' is a link. If so,
             # change it to point to the source of the link.
             if follow:
-                dest_status_nofollow = self._execute_remote_stat(dest_file, all_vars=task_vars, follow=False)
+                dest_status_nofollow = self._execute_remote_stat(dest_file, all_vars=task_vars, tmp=tmp, follow=False)
                 if dest_status_nofollow['islnk'] and 'lnk_source' in dest_status_nofollow.keys():
                     dest = dest_status_nofollow['lnk_source']
 
@@ -345,7 +345,8 @@ class ActionModule(ActionBase):
         if not module_return.get('checksum'):
             module_return['checksum'] = local_checksum
 
-        return module_return
+        result.update(module_return)
+        return result
 
     def _get_file_args(self):
         new_module_args = {'recurse': False}