Can you flesh out your description and testing done? See https://www.notion.so/reviewboard/Writing-Good-Change-Descriptions-10529e7c207743fa8ca90153d4b21fea#writinggoodchangedescriptions

We should probably explain why it is hidden instead of just stating that it is. e.g., 

This file was hidden because it is likely minified. Show content.

Single quotes for strings.

It is more Pythonic to do elif '.min.' in depot_filename: (and also more readable).

nit: blank line between these.

This only tests the cumulative diff (ie the squashed version of all the commits) case.
Can you add a a test to make sure it works for the individual commits as well?

nit: blank line between these.

nit: we do django template indentation a little differently: the indentation occurs inside the block tags. Additionally, HTML is indented one space (irrespective of the django tag indentation), e.g.:

{% elif file.hide and not show_deleted %}
{%  if file.hide_context == 'deleted' %}
 <tbody>
  <tr>
   <td colspan="4">
{%   if file.num_changes == 0 %}
{%    trans "..." %}

Let's expand this comment just a little bit. How about:

# Choose the most important information to show for why a
# file is hidden. If a minified file is deleted, prefer to
# show it as deleted.

I know it's not part of your change per se, but this is leftover debug output and can be removed.

Can we move these new tests to be at the end of this suite? Right now they break up a bunch of other more related tests.

How about "Testing get_diff_files hiding of deleted/minified files for a diffset with history"?
That line can wrap as needed.

Please change out the " quotes for ' quotes.

How about "Testing get_diff_files hiding of deleted/minified files for an individual commit"?
That line can wrap as needed.

Please change out the " quotes for ' quotes.

This needs to use an exact equality comparison operator (===)

The way this is laid out is a little bit error-prone (we're kind of interleaving the if/else clauses and HTML tags). We can simplify it a lot by pulling the tbody class name out into a variable:

{% definevar "tbody_class" %}{% spaceless %}
{%  if file.hide_context == "deleted" %}
deleted
{%  else %}
hidden
{%  endif %}
{% endspaceless %}{% enddefinevar %}

<tbody class="{{tbody_class}}">
 <tr>
  <td colspan="4">
{% if file.hide_context == "deleted" %}
    ...
{% endif %}
  </td>
 </tr>
</tbody>

This doesn't really make sense. Either a file is empty (no content) or minified (lots of content all squished together).
I think if a file is empty we should always show the "This is an empty file" line.

Please undo. This is here for debugging test failures.