Auto refresh dir contents

[habamax]

There is no way in vim to watch a file system for a changes...

Currently all dir contents is cashed and refresh happens only in some cases (some file ops).

Or user has to manually refresh if needed (with :edit command).

It would be nice to have some cache retention for, let say 5 minutes (should be configurable).

Thus if a user visits a buffer with vim-dir and cache is expired, it should refresh it.