-source of messages: a directory (Maildir) or a file. For a regular
-file, the location must have a C<E<lt>formatE<gt>:> prefix specifying
-one of the following formats: C<eml>, C<mboxrd>, C<mboxcl2>,
-C<mboxcl>, or C<mboxo>.
+source of messages: a directory (Maildir), a file, or a URL
+(C<imap://>, C<imaps://>, C<nntp://>, or C<nntps://>). URLs requiring
+authentication use L<git-credential(1)> to
+fill in the username and password.