Support iteration over command output in with_items.

When the output of a command is stored in a register, this will create a
stdout_lines field in the result object that contains stdout split into a list
of lines.  This list can then be iterated over using with_items.

lib/ansible/playbook/__init__.py

@@ -258,6 +258,8 @@ class PlayBook(object):
             facts = result.get('ansible_facts', {})
             self.SETUP_CACHE[host].update(facts)
             if task.register:
+                if 'stdout' in result:
+                    result['stdout_lines'] = result['stdout'].splitlines()
                 self.SETUP_CACHE[host][task.register] = result
 
         # flag which notify handlers need to be run

test/TestPlayBook.py

@@ -181,3 +181,20 @@ class TestPlaybook(unittest.TestCase):
        )
        play = ansible.playbook.Play(playbook, playbook.playbook[0], os.getcwd())
        assert play.hosts == ';'.join(('host1', 'host2', 'host3'))
+
+   def test_results_list(self):
+       # Test that we can iterate over the lines of a command's stdout in a register variable.
+       test_callbacks = TestCallbacks()
+       playbook = ansible.playbook.PlayBook(
+           playbook=os.path.join(self.test_dir, 'results_list.yml'),
+           host_list='test/ansible_hosts',
+           stats=ans_callbacks.AggregateStats(),
+           callbacks=test_callbacks,
+           runner_callbacks=test_callbacks
+       )
+       result = playbook.run()
+       self.assertIn('localhost', result)
+       self.assertIn('ok', result['localhost'])
+       self.assertEqual(result['localhost']['ok'], 6)
+       self.assertIn('failures', result['localhost'])
+       self.assertEqual(result['localhost']['failures'], 0)

test/results_list.yml

+---
+# Test iterating over lines of stdout stored in a register.
+- hosts: localhost
+  vars:
+    small_file: /etc/resolv.conf
+    temp_file: /tmp/ansible_result_list.tmp
+
+  tasks:
+  - action: command cat $small_file
+    register: result
+
+  - action: file dest=$temp_file state=absent
+
+  - action: shell echo '$item' >> $temp_file
+    with_items: ${result.stdout_lines}
+
+  - action: command diff $small_file $temp_file
+
+  - action: file dest=$temp_file state=absent