Refresh NERDTree and perform :CommandTFlush when window gains focus.

gvimrc

@@ -24,6 +24,35 @@ if has("gui_macvim")
   macmenu Window.Toggle\ Full\ Screen\ Mode key=<D-CR>
 endif
 
+if exists("loaded_nerd_tree")
+  augroup AuNERDTreeCmd
+  autocmd AuNERDTreeCmd FocusGained * call s:UpdateNERDTree()
+endif
+
+" NERDTree utility function
+function s:UpdateNERDTree(...)
+  let stay = 0
+
+  if(exists("a:1"))
+    let stay = a:1
+  end
+
+  if exists("t:NERDTreeBufName")
+    let nr = bufwinnr(t:NERDTreeBufName)
+    if nr != -1
+      exe nr . "wincmd w"
+      exe substitute(mapcheck("R"), "<CR>", "", "")
+      if !stay
+        wincmd p
+      end
+    endif
+  endif
+
+  if exists(":CommandTFlush") == 2
+    CommandTFlush
+  endif
+endfunction
+
 "-------------------------------------------
 "                 LOCAL CONFIG
 "-------------------------------------------