what's the `default` block? not sure I follow there. From the engines I've used I guess I expect something like this in the layout:

```
<% block content %>
Some default content
<% endblock %>
```

and then overriding in the child as:

```
<% block content %>
new content
<% endblock %>
```

if you had another child extending _that_ child, then it would just do the same and override again.

As far as a more terse single-line placeholder goes it would definitely be nice to have something, we could just detect <%- or <%= but that's a little hacky