Adjust 'path' ordering

Bram has decreed that ftplugin/ruby.vim should unconditionally inherit
"." and "" from the default global 'path'.  This change accounts for
that, preserving their position at the very end.  This change also
incidentally impacts asset files, which seems fine.

Author: tpope

autoload/rails.vim

@@ -4855,16 +4855,16 @@ function! s:map_gf() abort
 endfunction
 
 function! rails#update_path(before, after) abort
-  if &l:path =~# '\v^\.%(,/%(usr|emx)/include)=,,$'
-    let before = []
-    let after = []
+  if &l:path =~# '\v^\.%(,/%(usr|emx)/include)=,,$|^$'
+    let append = ''
+    let old = []
   else
-    let before = &l:path =~# '^\.\%(,\|$\)' ? ['.'] : []
-    let after = s:pathsplit(s:sub(&l:path, '^\.%(,|$)', ''))
+    let append = matchstr(&l:path, '\%(,\.\)\=\%(,,\)$')
+    let old = s:pathsplit(&l:path[0 : -len(append) - 1])
   endif
 
   let r = 'substitute(v:val, "^\\a\\a\\+:", "+&", "")'
-  let &l:path = s:pathjoin(s:uniq(before + map(a:before, r) + after + map(a:after, r)))
+  let &l:path = s:pathjoin(s:uniq(map(a:before, r) + old + map(a:after, r))) . append
 endfunction
 
 function! rails#sprockets_setup(type) abort