Fix IPV6 bracketing regexp

References: tpope#592

Author: tpope

autoload/rails.vim

@@ -1993,7 +1993,7 @@ function! rails#get_binding_for(pid) abort
       let binding = ''
     endif
   endif
-  let binding = substitute(binding, '^\(^[^[]*:.*):', '[\1]:', '')
+  let binding = substitute(binding, '^\(^[^[]*:.*\):', '[\1]:', '')
   if empty(binding)
     return ''
   endif