Bookmarks: wipe directory buffers on session autoload

References https://github.com/mhinz/vim-startify/issues/231

autoload/startify.vim

@@ -776,6 +776,7 @@ function! s:check_user_options(path) abort
   let session = a:path . s:sep .'Session.vim'
 
   if get(g:, 'startify_session_autoload') && filereadable(session)
+    execute 'silent bwipeout' a:path
     execute 'source' session
   elseif get(g:, 'startify_change_to_vcs_root')
     call s:cd_to_vcs_root(a:path)