This setting determines how much sanity checking, if any, the "fossil commit" and "fossil amend" commands do against check-in comments. Recognized values:

on

(Default) Check for bad syntax in check-in comments and offer the user a chance to continue editing for interactive sessions, or simply abort the commit if commit was entered using -m or -M

off

Do not do syntax checking of any kind

links

Similar to "on", except only check for bad hyperlinks

preview

Do all the same checks as "on" but also preview the check-in comment to the user during interactive sessions and provide an opportunity to accept or re-edit