Update file path out-of-band

[brichet]

Description

Renaming a file from the file system (not from jupyter) does not update the database.

Reproduce

Open a file in collaboration, rename it from the file system. The ContentManager is not happy because it looks for the former file path.

Renaming it from jupyterlab correctly update the file path in the database, though.

Expected behavior

The new file path to be used.

Context

[krassowski]

I guess we would need to (optimally) depend on https://github.com/gorakhargosh/watchdog/ or similar. Watching files cross-platform is not easy. In the repo at the bottom there is a list of other libraries that allow for that.

[davidbrochart]

Jupyverse uses watchfiles.

[krassowski]

Jupyverse uses watchfiles.

This package was previously named "watchgod"

Good one! Does not seem to support tracking renames yet though: samuelcolvin/watchfiles#201