I would prefer to report an error on unknown options to inform the user about the error. But with fstab there are options that davfs2 has to ignore because they may be required for other programs. To ignore some options (but not all) the C-functions used by davfs2 to parse the options would require a list of the options to ignore. With these x-something kind of options, whose number may grow indefinitely, this is no longer possible. For this reason I gave up. davfs2 will now ignore all unknown options. The change is in the CVS-sources and will make it into the next release.
Werner
