Is your feature request related to a problem? Please describe.

There is currently no way to download or upload a directory with the az storage fs interface. Since ADLS Gen2 is a hierarchical system, it needs to have a way to interact with directories as a first-class citizen. This was possible before with the az storage blob directory download command in the storage-preview extension.

Describe the solution you'd like

Add a new --recursive flag to az storage fs file download and az storage fs file upload commands. Or create new az storage fs directory download and az storage fs directory upload commands that work with directories recursively.

Describe alternatives you've considered

Enumerate the folder contents with az storage fs directory list, then parse it and call az storage fs file download separately (and recurse for subdirectories). This is infeasible because of the startup cost of starting a new az process for each file.

Additional context

While the new az storage fs interface is a clear improvement over az storage blob directory (for example directory listing doesn't take ages to run), this case is an obvious regression that has to be addressed for it to be usable at all.