set $VIMHOME handling symlinked vimrc; activate undofile

.gitignore

@@ -0,0 +1 @@
+undo/*

vimrc

@@ -1,6 +1,7 @@
 "==============================================================================
 " General Settings
 "==============================================================================
+let $VIMHOME=fnamemodify(resolve(expand("<sfile>")), ":p:h")
 set nocompatible
 syntax enable
 filetype plugin indent on
@@ -14,8 +15,8 @@ set softtabstop=4
 set ruler
 set showmatch
 if has("persistent_undo")
-    "set undodir=$VIMHOME/undo
-    "set undofile
+    set undodir=$VIMHOME/undo
+    set undofile
 endif
 set mouse=a
 set hlsearch