Merge branch 'js/get-short-oid-drop-cache'

A corner-case object name ambiguity while the sequencer machinery
is working (e.g. "rebase -i -x") has been (half) fixed.

* js/get-short-oid-drop-cache:
  get_oid(): when an object was not found, try harder
  sequencer: move stale comment into correct location
  sequencer: improve error message when an OID could not be parsed
  rebase -i: demonstrate obscure loose object cache bug