Call 'git submodule init' to add the new submodule to .git/config

autoload/vundle/installer.vim

@@ -209,7 +209,7 @@ func! s:sync(bang, bundle) abort
       let top_level = substitute(s:system('cd '.shellescape(g:bundle_dir).'; git rev-parse --show-toplevel'), '\n', '', 'g')
       let prefix    = substitute(s:system('cd '.shellescape(g:bundle_dir).'; git rev-parse --show-prefix'), '\n', '', 'g')
       let relative_path = prefix.substitute(a:bundle.path(), g:bundle_dir.'/', '', '')
-      let cmd = 'cd '.shellescape(top_level).'; git submodule add '.a:bundle.uri.' '.shellescape(relative_path)
+      let cmd = 'cd '.shellescape(top_level).'; git submodule add '.a:bundle.uri.' '.shellescape(relative_path).'; git submodule init'
     endif
   endif