title: Where are the instance variables coming from on the email-ext jelly/groovy scripts?
body: <p>The templates and examples provided by the email-ext plugin on jenkins reference variables such as <code>build, root, it</code>, etc.... Where are these variables coming from and where is the documentation on them? I understand to some extent that <code>it</code> is the reference to the plugin instance, but that's about where my understanding ends.</p>
  
  <p>If you need reference to the scripts you can see some examples here:
  <a href="https://github.com/jenkinsci/email-ext-plugin/tree/master/src/main/resources/hudson/plugins/emailext/templates" rel="noreferrer">https://github.com/jenkinsci/email-ext-plugin/tree/master/src/main/resources/hudson/plugins/emailext/templates</a></p>