Merge branch 'jt/de-global-bulk-checkin'

The bulk-checkin code used to depend on a file-scope static
singleton variable, which has been updated to pass an instance
throughout the callchain.

* jt/de-global-bulk-checkin:
  bulk-checkin: use repository variable from transaction
  bulk-checkin: require transaction for index_blob_bulk_checkin()
  bulk-checkin: remove global transaction state
  bulk-checkin: introduce object database transaction structure

diff --cc odb.h
Simple merge