add topics and branches

potatoe/models.py

@@ -24,6 +24,20 @@ class Context(models.Model):
     def __str__(self):
         return self.name
 
+class Topic(models.Model):
+    """Describes a topic; it is linked to several projects/contexts and has a tracker to see
+    what has been done."""
+
+    name = models.CharField(max_length=255)
+    projects = models.ManyToManyField('Project', related_name='topics')
+    contexts = models.ManyToManyField('Context', related_name='topics')
+
+class Branch(models.Model):
+    """Describes a branch (ie. an option) inside a topic."""
+
+    name = models.CharField(max_length=255)
+    topic = models.ForeignKey(Topic)
+
 class Task(models.Model):
     """
     Describes something that has to be done.