[FR] Initialize dvc in sub-directory of a git repo

[Tradunsky]

For the case of using monorepo it can be useful to have dvc initialized per model dir, but if you try to init it under a sub-dir it says:

ERROR: failed to initiate dvc - monorepo-models/an-ordinary-model is not tracked by any supported scm tool (e.g. git). Use --no-scm if you don't want to use any scm.

[Tradunsky]

An option is to init dvc without scm, but @shcheklein says that there is an implication that you won't be able to use features that expect branches, tags, or commits exist - e.g. show metrics - it needs Git to analyze different versions.

[efiop]

@Tradunsky Looks like a duplicate of #2349 . If you agree, let's close this one and move the discussion there.