Don't write revisioned in merge test
Add ?rev to jiraph.debug
Fix typo
Add some merge tests that actually merge
Add test for criss-cross edges
Don't need a phantom layer for edge-merging
When reassembling a node, read *before* the merge revision
Rename layer inside ruminate-merge to merge-layer
When unmerging a node all the way, don't create merge edges to itself
Fix get-revisions for resettable layer
Add basic unmerging test