Your target selectors may use this pseudo-selector
to reference the element that triggered the change.
The origin element is automatically set to a link that is being followed
or form that is being submitted. When updating fragments
programmatically through up.render() you may pass an origin element as an { origin } option.
Even without using an :origin reference, the
origin is considered
when matching fragments in the current page.
Shorthand
Instead of :origin you may also use the ampersand character (&).
You may be familiar with the ampersand from the Sass
CSS preprocessor.
