Merge pull request #3871 from urbit/lf/graph-pull-cleanup

graph-pull-hook: only archive if we have graph

pkg/arvo/app/graph-pull-hook.hoon

@@ -36,6 +36,7 @@
   |=  [=resource =tang]
   ^-  (quip card _this)
   :_  this
+  ?.  (~(has in get-keys:gra) resource)  ~
   =-  [%pass /pull-nack %agent [our.bowl %graph-store] %poke %graph-update -]~
   !>  ^-  update:store
   [%0 now.bowl [%archive-graph resource]]

pkg/arvo/lib/graph.hoon

@@ -45,4 +45,12 @@
   ^-  update-log:store
   %+  scry-for  update-log:store
   /update-log-subset/(scot %p entity.res)/[name.res]/(scot %da start)/'~'
+::
+++  get-keys
+  ^-  resources
+  =+  %+  scry-for  ,=update:store
+      /keys
+  ?>  ?=(%0 -.update)
+  ?>  ?=(%keys -.q.update)
+  resources.q.update
 --