how: move `.dvc` files when their data is not checked out

From https://github.com/iterative/dvc/issues/7318:

Assume that the file video121.mpeg is tracked by video121.mpeg.dvc. If one wants to move it to folder subdir it depends on whether video121.mpeg is checked out.

1. If video121.mpeg is checked out, then dvc move video121.mpeg subdir/ must be used to do it safely.

2. If video121.mpeg is not checked out, then mv video121.mpeg.dvc subdir/ can be used. dvc move video121.mpeg.dvc subdir/ does not work.

Can we document somewhere that doing mv video121.mpeg.dvc subdir/ is safe when files aren’t checked out? Possible places to document this:

• https://dvc.org/doc/user-guide/how-to/update-tracked-data
• https://dvc.org/doc/command-reference/move

UPDATE: Jump to https://github.com/iterative/dvc.org/issues/3354#issuecomment-1081293810 below.

[iesahin]

I believe mentioning this may encourage users to try an undefined behavior. Saying “mv src.dvc target/ is safe if you update .gitignore manually” looks like encouraging a bad practice IMHO. If they are savvy enough to know DVC internals in such a degree, I think they don’t need check the manual anyway.

[dberenbaum]

Sounds good. The core issue is already there in #7318, so let’s just close this one.