Import-url no download

[dmpetrov]

In some cases, user needs to keep connection to a storage file in a repository but does not need to work with the model (or data) right now. --no-exec option is not enough because user needs to track if file changes (cloud checksums are needed) and user should have an ability to check this status in the future.

So, we need a more granular import-url:

• [ ] dvc-import --no-download (the same as --etags-only in #6485) which is like --no-exec but it sets cloud storage checksums
• [ ] Check for dvc-import (how about --check-only option?) which checks if file was changed in cloud storage (exit status not zero) or file is the same (zero exist status). Can we do this with status btw?

This issue is related to #6485

[casperdcl]

dvc import --no-download makes sense. Meanwhile for dvc import --check-only... not sure I follow, but sounds more like a use case for dvc status or #5369?

[skshetry]

dvc import --no-download makes sense. Meanwhile for dvc import --check-only... not sure I follow, but sounds more like a use case for dvc status or #5369?

dvc import and dvc import-url created stages are frozen by default, so dvc status will not return any outputs (unless we opt to make them non-frozen in case of --no-download which I think is a different behaviour than default imports which we should not do).

The --check-only might fit better in dvc update command.

[dberenbaum]

Yes, either update or status flags would make sense. We don't want users to have to recreate the whole import-url to find out whether the source has changed.