[2375] Add support for clearing all keys to c.remove_field

This change makes the second "value" argument optional. Also hooked
up the "Clear all" buttons in the facet navigation.

ckan/controllers/package.py

@@ -135,9 +135,18 @@ def drill_down_url(alternative_url=None, **by):
 
         c.drill_down_url = drill_down_url
 
-        def remove_field(key, value):
+        def remove_field(key, value=None):
+            """
+            Remove a key from the current search parameters. A specific
+            key/value pair can be removed by passing a second value argument
+            otherwise all pairs matching the key will be removed.
+            """
             params = list(params_nopage)
-            params.remove((key, value))
+            if value:
+                params.remove((key, value))
+            else:
+              [params.remove((k, v)) for (k, v) in params[:] if k==key]
+
             return search_url(params)
 
         c.remove_field = remove_field

ckan/templates/snippets/facet_list.html

@@ -24,7 +24,7 @@
   
   -->
 <section class="module" xmlns:py="http://genshi.edgewall.org/" py:with="items=h.unselected_facet_items(name, 10)">
-  <h2 class="heading">${h.facet_title(title)} <a class="btn btn-small">Clear All</a></h2>
+  <h2 class="heading">${h.facet_title(title)} <a href="${c.remove_field(name)}" class="btn btn-small">Clear All</a></h2>
   <nav>
     <ul class="unstyled nav nav-simple">
       <py:for each="item in items">