installation validation

[Thien-Thi Nguyen]

A local Gnus user that i support did something "mysterious"
and now some of the nnml groups seem to be (i'm not sure)
agentized, or at least relocated from dir

  ~/Mail/mail

to dir

  ~/News/agent/nnml/unnamed/mail

Another (possibly unrelated) result is that attempts to retrieve
mail (using ‘g’) from one of the IMAP sources now consistently
shows "Mail source (DETAILS) error (IMAP error: Internal error
occurred. Error report written to server log [TIMESTAMP])".  Hmm...

I'd like to restore previous known-good state if possible.
How can i validate (for self-consistency and well-formedness)
the structure of the Mail and News subdirs?

I imagine, say, ‘M-x validate-gnus-installation RET’ to either
display a message "Everything OK" or pop up a buffer w/ some
diagnostic info that might help to track down the "mysterious"
goings on.

Dare i hope for such a beast to exist?

Presuming the answer is "no, until Someone writes it", the
next questions are:
- How would i go about diagnosing the current situation?
- What would be the best way to repair the Mail and News
  dirs and restore mail-retrieval functionality?