Fixed #5908 -- Added {% resetcycle %} template tag.

Thanks to Simon Litchfield for the report, Uninen for the initial
patch, akaihola, jamesp, b.schube, and Florian Appoloner for
subsequent patches, tests, and documentation.

docs/ref/templates/builtins.txt

@@ -185,6 +185,9 @@ call to ``{% cycle %}`` doesn't specify ``silent``::
     {% cycle 'row1' 'row2' as rowcolors silent %}
     {% cycle rowcolors %}
 
+You can use the :ttag:`resetcycle` tag to make a ``{% cycle %}`` tag restart
+from its first value when it's next encountered.
+
 .. templatetag:: debug
 
 ``debug``
@@ -994,6 +997,57 @@ attribute, allowing  you to group on the display string rather than the
 ``{{ country.grouper }}`` will now display the value fields from the
 ``choices`` set rather than the keys.
 
+.. templatetag:: resetcycle
+
+``resetcycle``
+--------------
+
+.. versionadded:: 1.11
+
+Resets a previous `cycle`_ so that it restarts from its first item at its next
+encounter. Without arguments, ``{% resetcycle %}`` will reset the last
+``{% cycle %}`` defined in the template.
+
+Example usage::
+
+    {% for coach in coach_list %}
+        <h1>{{ coach.name }}</h1>
+        {% for athlete in coach.athlete_set.all %}
+            <p class="{% cycle 'odd' 'even' %}">{{ athlete.name }}</p>
+        {% endfor %}
+        {% resetcycle %}
+    {% endfor %}
+
+This example would return this HTML::
+
+    <h1>José Mourinho</h1>
+    <p class="odd">Thibaut Courtois</p>
+    <p class="even">John Terry</p>
+    <p class="odd">Eden Hazard</p>
+
+    <h1>Carlo Ancelotti</h1>
+    <p class="odd">Manuel Neuer</p>
+    <p class="even">Thomas Müller</p>
+
+Notice how the first block ends with ``class="odd"`` and the new one starts
+with ``class="odd"``. Without the ``{% resetcycle %}`` tag, the second block
+would start with ``class="even"``.
+
+You can also reset named cycle tags::
+
+    {% for item in list %}
+        <p class="{% cycle 'odd' 'even' as stripe %} {% cycle 'major' 'minor' 'minor' 'minor' 'minor' as tick %}">
+            {{ item.data }}
+        </p>
+        {% ifchanged item.category %}
+            <h1>{{ item.category }}</h1>
+            {% if not forloop.first %}{% resetcycle tick %}{% endif %}
+        {% endifchanged %}
+    {% endfor %}
+
+In this example, we have both the alternating odd/even rows and a "major" row
+every fifth row. Only the five-row cycle is reset when a category changes.
+
 .. templatetag:: spaceless
 
 ``spaceless``

docs/releases/1.11.txt

@@ -313,6 +313,9 @@ Templates
   so you can unpack the group object directly in a loop, e.g.
   ``{% for grouper, list in regrouped %}``.
 
+* Added a :ttag:`resetcycle` template tag to allow resetting the sequence of
+  the :ttag:`cycle` template tag.
+
 Tests
 ~~~~~