`--md-hist` / volflag `md_hist` specifies where to put old
versions of markdown files when edited using the web-ui;
* `s` = create `.hist` subfolder next to the markdown file
(the default, both previously and now)
* `v` = use the volume's hist-path, either according to
`--hist` or the `hist` volflag. NOTE: old versions
will not be retrievable through the web-ui
* `n` = nope / disabled; overwrite without backup
fc88341820