group-push-hook: kick members who are not subscribed

If a ship breaches, it may no longer be subscribed to the group, but
still be in it. This causes DM breakage amongst other things. To fix it,
we loop over the incoming subscriptions and kick everyone who is a part
of a group, but not subscribed to it.

pkg/arvo/app/group-push-hook.hoon

@@ -36,7 +36,68 @@
 ++  on-init  on-init:def
 ++  on-save  !>(~)
 ++  on-load    on-load:def
-++  on-poke   on-poke:def
+++  on-poke   
+  |=  [=mark =vase]
+  ^-  (quip card _this)
+  |^
+  ?.  =(mark %sane)
+    (on-poke:def mark vase)
+  [sane this]
+  ::
+  ++  scry-sharing
+    .^  (set resource)
+      %gx
+      (scot %p our.bowl)
+      %group-push-hook
+      (scot %da now.bowl)
+      /sharing/noun
+    ==
+  ::
+  ++  sane
+    ^-  (list card)
+    %+  murn
+      ~(tap in scry-sharing)
+    |=  rid=resource
+    ^-  (unit card)
+    =/  u-g=(unit group)
+      (scry-group:grp rid)
+    ?~  u-g 
+      `(poke-us %remove rid)
+    =*  group  u.u-g
+    =/  subs=(set ship)
+      (get-subscribers-for-group rid)
+    =/  to-remove=(set ship)
+      (~(dif in members.group) subs)
+    ?~  to-remove  ~
+    `(poke-store %remove-members rid to-remove)
+  ::
+  ++  poke-us
+    |=  =action:push-hook
+    ^-  card
+    =-  [%pass / %agent [our.bowl %group-push-hook] %poke -]
+    push-hook-action+!>(action)
+  ::
+  ++  poke-store
+    |=  =update:store
+    ^-  card
+    =+  group-update+!>(update)
+    [%pass /sane %agent [our.bowl %group-store] %poke -]
+  ::
+  ++  get-subscribers-for-group
+    |=  rid=resource
+    ^-  (set ship)
+    =/  target=path
+      (en-path:resource rid)
+    %-  ~(gas in *(set ship))
+    %+  murn
+      ~(val by sup.bowl)
+    |=  [her=ship =path]
+    ^-  (unit ship)
+    ?.  =(path resource+target)
+      ~
+    `her
+  --
+
 ++  on-agent  on-agent:def
 ++  on-watch    on-watch:def
 ++  on-leave    on-leave:def

pkg/arvo/ted/sane.hoon

@@ -8,6 +8,7 @@
   ^-  (list term)
   :~  %graph-pull-hook
       %group-pull-hook
+      %group-push-hook
   ==
 ::
 ++  poke-all-sane