Initial simple separation to get the process of extracting dvc-objects
and dvc-data packages out of dvc.
dvc-objects is for:
* defining base Object (aka HashFile) and ObjectDB
* providing tools to work with those objects (check/transfer/etc)
* etc
dvc-data is for:
* defining higher level objects (e.g. Tree)
* bulding objects from the workspace (aka staging)
* projecting objects back into the workspace (aka checkout)
* comparing Tree objects (aka diff)
* defining misc object databases (e.g LocalObjectDB)
* higher-level transfer (e.g. with Tree indexes)
* etc
For example, the objects we use in run-cache are based on dvc-objects
and not on dvc-data, as they have absolutely nothing to do with data
management.
There are still some mixups in the code that will be addressed in the
followups.
* dvc: get rid of DirInfo
DirInfo was created before we had proper objects, as a way to have a
structure that represents a staged directory. Right now we have a
dedicated Tree object that is specifically meant for that.
As a result, HashInfo no longer needs to have dir_info and we no longer
need `get_hash/get_dir_hash` helpers.
* objects: move Tree into tree.py
Ruslan Kuprieiev
Batuhan Taskaya