I'm working with CentOS 7, and Vim 7.4, :setl--- Local option values ---  autoindent          define=             include=            path=               softtabstop=4--autoread            errorformat=        keywordprg=         readonly            syntax=cpp  cindent             filetype=cpp        makeprg=            shiftwidth=4        tabstop=4  cryptmethod=        grepprg=            number              smartindent         tags=  comments=sO:* -,mO:*  ,exO:*/,s1:/*,mb:*,ex:*/,://  fileencoding=utf-8  formatoptions=croql  omnifunc=ccomplete#Complete  undolevels=-123456:versionVIM - Vi IMproved 7.4 (2013 Aug 10, compiled Jun 10 2014 06:55:55)Included patches: 1-160Modified by <bugzilla@redhat.com>Compiled by <bugzilla@redhat.com>My main question:What does the -- prefix in front of the 'autoread' option mean?Next question:Since I could find no help on this anywhere, are there any other prefixes that I should know about?
When I view local options (i.e. :setlocal) - what do the odd prefixes (i.e. '--') mean?
options
From :h :setlocal:                                                        :setl :setlocal:setl[ocal] ...         Like :set but set only the value local to the                        current buffer or window.  Not all options have a                        local value.  If the option does not have a local                        value the global value is set.                        With the all argument: display local values for all                        local options.                        Without argument: Display local values for all local                        options which are different from the default.                        When displaying a specific local option, show the                        local value.  For a global/local boolean option, when                        the global value is being used, -- is displayed                        before the option name.