R1:afd2ace0dc9c

Apply inverse edge edits after committing primary object edits

Summary:
Fixes T13082. When you create a revision (say, `D111`) with `Ref T222` in the body, we write a `D111 -> T222` edge ("revision 111 references task 222") and an inverse `T222 -> D111` edge ("task 222 is referenced by revision 111").

We also apply a transaction to `D111` ("alice added a task: Txxx.") and an inverse transaction to `T222` ("alice added a revision: Dxxx").

Currently, it appears that the inverse transaction can sometimes…