I downloaded the user manual for the Repository module and have two questions.

1.  How would I specify that a field is required or optional?  Or are TITLE and FILE always required?  (I want FILE to be optional, if possible.)

2.  Can I apply any logic to a template?  For instance, if an item has no Summary, is there any way to skip part of the display template?

Correct way to do it .. good job.

On you second question, you can certainly do it. In the template.html file wrap a div around the section you want to hide, then you can add custom javascript to your header.html file ( you would want to add it to the header or footer templates so that the javascript is only output to the page once. If you add it to the template.html file it will be output multiple times, once for each item ). In the javascript, add a function that will set the style.display to 'none' if the summary data is blank, something like

HideIfBlank(itemId, divId)

then, finally at the bottom of your template.html file, add a javascript call to the function which will look at the itemId.value and if it's blank set the divId.style.display to 'none'.

That should do it :)

If you have any problems, let me know