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.

tests/template_tests/syntax_tests/test_resetcycle.py

@@ -0,0 +1,95 @@
+from django.template import TemplateSyntaxError
+from django.test import SimpleTestCase
+
+from ..utils import setup
+
+
+class ResetCycleTagTests(SimpleTestCase):
+
+    @setup({'resetcycle01': "{% resetcycle %}"})
+    def test_resetcycle01(self):
+        with self.assertRaisesMessage(TemplateSyntaxError, "No cycles in template."):
+            self.engine.get_template('resetcycle01')
+
+    @setup({'resetcycle02': "{% resetcycle undefinedcycle %}"})
+    def test_resetcycle02(self):
+        with self.assertRaisesMessage(TemplateSyntaxError, "Named cycle 'undefinedcycle' does not exist."):
+            self.engine.get_template('resetcycle02')
+
+    @setup({'resetcycle03': "{% cycle 'a' 'b' %}{% resetcycle undefinedcycle %}"})
+    def test_resetcycle03(self):
+        with self.assertRaisesMessage(TemplateSyntaxError, "Named cycle 'undefinedcycle' does not exist."):
+            self.engine.get_template('resetcycle03')
+
+    @setup({'resetcycle04': "{% cycle 'a' 'b' as ab %}{% resetcycle undefinedcycle %}"})
+    def test_resetcycle04(self):
+        with self.assertRaisesMessage(TemplateSyntaxError, "Named cycle 'undefinedcycle' does not exist."):
+            self.engine.get_template('resetcycle04')
+
+    @setup({'resetcycle05': "{% for i in test %}{% cycle 'a' 'b' %}{% resetcycle %}{% endfor %}"})
+    def test_resetcycle05(self):
+        output = self.engine.render_to_string('resetcycle05', {'test': list(range(5))})
+        self.assertEqual(output, 'aaaaa')
+
+    @setup({'resetcycle06': "{% cycle 'a' 'b' 'c' as abc %}"
+                            "{% for i in test %}"
+                            "{% cycle abc %}"
+                            "{% cycle '-' '+' %}"
+                            "{% resetcycle %}"
+                            "{% endfor %}"})
+    def test_resetcycle06(self):
+        output = self.engine.render_to_string('resetcycle06', {'test': list(range(5))})
+        self.assertEqual(output, 'ab-c-a-b-c-')
+
+    @setup({'resetcycle07': "{% cycle 'a' 'b' 'c' as abc %}"
+                            "{% for i in test %}"
+                            "{% resetcycle abc %}"
+                            "{% cycle abc %}"
+                            "{% cycle '-' '+' %}"
+                            "{% endfor %}"})
+    def test_resetcycle07(self):
+        output = self.engine.render_to_string('resetcycle07', {'test': list(range(5))})
+        self.assertEqual(output, 'aa-a+a-a+a-')
+
+    @setup({'resetcycle08': "{% for i in outer %}"
+                            "{% for j in inner %}"
+                            "{% cycle 'a' 'b' %}"
+                            "{% endfor %}"
+                            "{% resetcycle %}"
+                            "{% endfor %}"})
+    def test_resetcycle08(self):
+        output = self.engine.render_to_string('resetcycle08', {'outer': list(range(2)), 'inner': list(range(3))})
+        self.assertEqual(output, 'abaaba')
+
+    @setup({'resetcycle09': "{% for i in outer %}"
+                            "{% cycle 'a' 'b' %}"
+                            "{% for j in inner %}"
+                            "{% cycle 'X' 'Y' %}"
+                            "{% endfor %}"
+                            "{% resetcycle %}"
+                            "{% endfor %}"})
+    def test_resetcycle09(self):
+        output = self.engine.render_to_string('resetcycle09', {'outer': list(range(2)), 'inner': list(range(3))})
+        self.assertEqual(output, 'aXYXbXYX')
+
+    @setup({'resetcycle10': "{% for i in test %}"
+                            "{% cycle 'X' 'Y' 'Z' as XYZ %}"
+                            "{% cycle 'a' 'b' 'c' as abc %}"
+                            "{% ifequal i 1 %}"
+                            "{% resetcycle abc %}"
+                            "{% endifequal %}"
+                            "{% endfor %}"})
+    def test_resetcycle10(self):
+        output = self.engine.render_to_string('resetcycle10', {'test': list(range(5))})
+        self.assertEqual(output, 'XaYbZaXbYc')
+
+    @setup({'resetcycle11': "{% for i in test %}"
+                            "{% cycle 'X' 'Y' 'Z' as XYZ %}"
+                            "{% cycle 'a' 'b' 'c' as abc %}"
+                            "{% ifequal i 1 %}"
+                            "{% resetcycle XYZ %}"
+                            "{% endifequal %}"
+                            "{% endfor %}"})
+    def test_resetcycle11(self):
+        output = self.engine.render_to_string('resetcycle11', {'test': list(range(5))})
+        self.assertEqual(output, 'XaYbXcYaZb')