undo-tree-mode doesn't work with nXhtml

[Ethan Glasser-Camp]

In emacs -Q, having done (require 'undo-tree) and (global-undo-tree-mode) in ielm, I found a file called foo.djhtml and activated django-html-mumamo-mode.

In this buffer I had text like this:

{% extends "base.html" %}

{% block scripts %}
{{ var1 }}
{{ var2 }}
{% endblock %}

{% block content %}
  Hi!
{% endblock %}

I moved to the two variables var1 and var2 and hit Tab, indent-for-tab-command. This inserted two spaces before them. Then I moved point down to {% block content %}. When I hit C-_ (undo-tree-undo), the first time it works as expected -- deleting the two spaces before var2. The second time I get "No further undo information".

Pressing M-_ (undo-tree-redo) gets "No further redo information".