Add sage-like functionality a la 4chan

When reply to a post, you can uncheck "bump" and it will not bump the
thread to the top of the board.

This is useful for the OP, too, because it allows for "permasage"
functionality which is useful for moderators.

Finally, there is also "autosink" functionality. After a per-board
threshhold of posts, a thread will stop bumping.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

board/models.py

@@ -47,6 +47,9 @@ class Board(models.Model):
     # The amount of time that users from the same IP address are allowed to make
     # consecutive posts
     post_cooldown = models.DurationField(default=timedelta(seconds=60))
+    # Auto-sink threshhold. This is the number of replies that a thread can have
+    # before it stops being bumped.
+    autosink = models.IntegerField(default=300)
 
     @property
     def threads(self):
@@ -89,6 +92,9 @@ class Post(models.Model):
         width_field="image_width",
         height_field="image_height",
     )
+    # Bump - if this post is an OP, determines whether the OP can be bumped. If
+    # this post is not an OP, determines whether the thread SHOULD be bumped.
+    bump = models.BooleanField(default=True)
     # Thumbnail
     thumbnail = models.ImageField(upload_to=thumbs_upload, editable=False, null=True)
     # Original image name
@@ -172,8 +178,13 @@ def post_created(sender, instance, created, **kwargs):
     if created:
         if instance.op:
             # Update the bump
-            instance.op.last_bump = timezone.now()
-            instance.op.save()
+            if (
+                instance.bump
+                and instance.op.bump
+                and instance.op.replies.count() < instance.board.autosink
+            ):
+                instance.op.last_bump = timezone.now()
+                instance.op.save()
         else:
             # Prune threads for the board
             instance.board.prune_threads()