By splitting dvc.cli into a module, we'll be able to share cli-related
utilities, split parser-related stuffs into smaller parts, improve
reusability and improve API for command extensions in the future.
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.
Intermediate PR in removing path_info from our code base.
It is completely removed from the main codebase and is still
being used in tests, which will be migrated in the followups.
For fs-specific simple path manipulation, we've introduced
`fs.path` helper (similar to `os.path`).
Fixes#6774
Nikita Kodenko
Saugat Pachhai (सौगात)
Ruslan Kuprieiev
Batuhan Taskaya
