Hi.

Attached is a proposed patch to csv-mode.el in GNU ELPA which adds CSV
separator guessing functionality to CSV mode.

It adds two new commands: `csv-guess-set-separator' that automatically
guesses and sets the CSV separator of the current buffer, and
`csv-set-separator' for setting it manually.

The idea is that `csv-guess-set-separator' can be useful to add to the
mode hook to have CSV mode guess and set the separator automatically
when visiting a buffer:

  (add-hook 'csv-mode-hook 'csv-guess-set-separator)

Been using it myself for the past weeks and have been happy with it so
far.