user-guide: clearly specify that state db is only used locally

[dmpetrov]

Sometimes people do not understand that SQLite is used only for optimization and they think that DVC uses a binary format (please use translate): https://www.facebook.com/permalink.php?story_fbid=1151521948337039&id=100004377340065&comment_id=1151533428335891&reply_comment_id=1153257634830137

Why don't we make it clear and extract .dvc/status file outside DVC project like /var/dvc/my-project-SOME_UNIQ_ID?

[efiop]

We will have then somehow uniquely identify that state db, so we'll have to store that info in our project, which only complicates things, otherwise, we won't be able to find state db when dvc repo is simply moved from one local directory to another. This is not worth bothering with, in my opinion. That guy just misread something and could've misread even if we would to extract state somewhere outside :)

[shcheklein]

@dmpetrov @efiop how about we just improve the documentation? Probably he stumbled upon SQLLite in our user guide, right? Or we have other places mentioning this?

[dmpetrov]

It is an important question since it is related to DVC "philosophy" of being an open format.
We should put this high on the docs.

An entry paragraph in needed in User Guide. Probably it is a good place for this info.

[efiop]

Agreed, moved to dvc.org.

[shcheklein]

I think it's solved since we moved SQLLite files under .dvc/tmp now.