Lua: extend pandoc.system module.

[tarleb]

The module now has the additional functions list_directory,
make_directory, and remove_directory. This makes it easier to write
cross-platform scripts that need to inspect or modify the file system.

[tarleb]

Motivation: https://groups.google.com/g/pandoc-discuss/c/l4os8uJVm1o/m/gWMtsPFAAgAJ

[jgm]

I guess the main use for create/delete directory would be to create temporary directories? In that case, I wonder if it would be better to export functions that do that? I don't think the Lua interface contains general-purpose functions to create and delete files (or does it?), so it seems a bit odd to have such functions for directories.

[tarleb]

Lua has os.remove and os.rename. Files can be created with io.open, but directories cannot be created with standard library functions: the C standard only knows about files, not directories.

I imagine that folder creation might be handy for some custom writer authors. But I admit that I never needed any of those new functions, as the pandoc.system.with_temporary_directory function was enough for my use-cases.