Previously, widgets were reading variables from themselves or their
cascaded ancestors. That means that if a widget sets a variable and
then reads the same variable, it will get the same variable back. That
sounds reasonable, until you consider a widget that wants to modify a
variable - eg the tiddler macro. For example:
```
<$tiddler tiddler={{!!report}}>
<$transclude mode="block" />
</$tiddler>
```
Here we first evaluate the `{{!!report}}` reference, which involves
reading the currentTiddler variable, looking up the tiddler, and
retrieving it’s `report` field. The next the tiddler widget is
refreshed, it will use the newly set currentTiddler as the basis for
resolving the `{{!!reference}}` reference.
The fix is to get variables from ancestors, but continue to set them on
ourselves.
e60fc9f81f