Enhancement - Supports '--' on the command line

- Using '--' on the command line separates the left hand side, where
  task is free to interpret arguments in the usual way, and the right
  hand side, which is then assumed to be part of the task description,
  and is not interpreted by task.

html/advanced.html

@@ -485,6 +485,18 @@ on_white    on_bright_white</code></pre>
                   Note also that this capability does depend on whether your terminal
                   program can display these colors.
                 </p>
+
+                <strong>% task add project:Home -- pri:H +tag /from/to/</strong>
+                <p>
+                  The -- argument can be used to tell task to stop interpreting
+                  the command line arguments.  In the example above, a new task
+                  is added for the project 'Home', then the -- argument appears,
+                  and therefore all remaining arguments are part of the
+                  description.  In this case, the description is "pri:H +tag
+                  /from/to/".  This is one way to override task's interpretation
+                  of the command line.  The other way is to put the entire
+                  description in quotes.
+                </p>
               </div>
 
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