doc: better document the template property in the request object.

Author: rouilj

doc/glossary.txt

@@ -81,13 +81,19 @@ Roundup Glossary
 
    template
 
-      this term has two meanings depending on context.
+      this term has three meanings depending on context.
 
       It refers to files that are processed by a templating engine to
       produce output suitable for machine or human consumption. For
       example a template could produce a html page that includes the
       name of the user.
 
+      It is an property of the request object in the templating
+      system. Templates that are used with a specific class (e.g.
+      ``issue.item.html``) will have this entry set to the middle
+      element (``item`` in this example). For templates like
+      ``home.html`` the element will be set to the empty string.
+
       It also can mean a **Tracker template**. This is a set of files
       used to install a new tracker. Tracker templates define a
       tracker with a particular look and feel, :term:`schema`,

doc/reference.txt

@@ -2735,7 +2735,10 @@ The following variables are available to templates.
   - "user" a HTMLItem instance for the current user
   - "language" as determined by the browser or configuration
   - "classname" the current classname (possibly None)
-  - "template" the current template (suffix, also possibly None)
+  - "template" the current template (e.g. for the ``issue.item.html``
+    template the template would be the ``item`` suffix on the
+    classname. It can also be the empty string (e.g. with the
+    ``home.html`` template).
 **config**
   This variable holds all the values defined in the tracker config.ini
   file (e.g. TRACKER_NAME, etc.)