The 'whence' field in 'struct object_info' has been removed. The
backend-specific object information retrieval has been refactored into
an opt-in 'struct object_info_source' structure.
* ps/odb-drop-whence:
odb: document object info fields
odb: drop `whence` field from object info
treewide: convert users of `whence` to the new source field
odb: add `source` field to struct object_info_source
odb: make backend-specific fields optional
packfile: thread odb_source_packed through packed_object_info()
a9d2d2acde