Pass description as positional argument.

Similarly to #134, passing description via description:{description}
doesn't appear to be documented and can lead to problems.

See GothenburgBitFactory/bugwarrior#733 and consider the following scenario:

```sh
$ task --version
2.5.1
$ task add description:"depends filter does not work with ID"
The expression could not be evaluated.
$ task add "depends filter does not work with ID"
Created task 1.
```

I've tried variations of the previous with various quoting and shells
and have gotten the same result.

Author: ryneeverett

taskw/test/test_utils.py

@@ -105,22 +105,25 @@ def test_ordering(self):
 
     def test_taskwarrior_null_encoding_bug_workaround(self):
         task = {
+            'description': 'arbitrary description',
             'priority': ''
         }
-        actual_encoded = encode_task_experimental(task)[0]
+        actual_encoded = encode_task_experimental(task)[1]
         expected_encoded = "priority:"
 
         assert actual_encoded == expected_encoded
 
     def test_encodes_dates(self):
         arbitrary_date = datetime.date(2014, 3, 2)
         task = {
+            'description': 'arbitrary description',
             'arbitrary_field': arbitrary_date
         }
 
         actual_encoded_task = encode_task_experimental(task)
         expected_encoded_task = encode_task_experimental(
             {
+                'description': 'arbitrary description',
                 'arbitrary_field': arbitrary_date.strftime(DATE_FORMAT)
             }
         )
@@ -130,12 +133,14 @@ def test_encodes_dates(self):
     def test_encodes_naive_datetimes(self):
         arbitrary_naive_datetime = datetime.datetime.now()
         task = {
+            'description': 'arbitrary description',
             'arbitrary_field': arbitrary_naive_datetime
         }
 
         actual_encoded_task = encode_task_experimental(task)
         expected_encoded_task = encode_task_experimental(
             {
+                'description': 'arbitrary description',
                 'arbitrary_field': (
                     arbitrary_naive_datetime
                     .replace(tzinfo=dateutil.tz.tzlocal())
@@ -152,12 +157,14 @@ def test_encodes_zoned_datetimes(self):
             tzinfo=arbitrary_timezone
         )
         task = {
+            'description': 'arbitrary description',
             'arbitrary_field': arbitrary_zoned_datetime
         }
 
         actual_encoded_task = encode_task_experimental(task)
         expected_encoded_task = encode_task_experimental(
             {
+                'description': 'arbitrary description',
                 'arbitrary_field': (
                     arbitrary_zoned_datetime
                     .astimezone(pytz.utc).strftime(DATE_FORMAT)

taskw/test/test_warrior.py

@@ -49,3 +49,12 @@ def test_add_task_recurs(self):
         assert tasks['pending'][0]['recur'] == 'weekly'
         assert tasks['pending'][0]['parent'] is not None
 
+    def test_add_task_depends_keyword(self):
+        """Add a task with description beginning with keyword "depends".
+        See https://github.com/ralphbean/bugwarrior/issues/733.
+        """
+        self.taskwarrior.task_add('depends filter does not work with IDs')
+        tasks = self.taskwarrior.load_tasks()
+        assert len(tasks['pending']) == 1
+        assert (tasks['pending'][0]['description']
+                == 'depends filter does not work with IDs')

taskw/utils.py

@@ -134,7 +134,7 @@ def encode_task_experimental(task):
         task[k] = encode_task_value(k, task[k])
 
     # Then, format it as a string
-    return [
+    return [task.pop('description')] + [
         "%s:\"%s\"" % (k, v) if v else "%s:" % (k, )
         for k, v in sorted(task.items(), key=itemgetter(0))
     ]