Fix: the config never has chance to save Global source if XDG source exists.

Merged username-removed-94717 requested to merge fix_XDG into master

I got a little problem and trace it to here(line 134~137). The logic there is a little different with line 107~113.

OK, then, here is the steps of my problem:

  1. Open Settings
  2. Go "Git" node/page
  3. Click "Global"
  4. Change "AutoCrlf"
  5. Push "Apply" button

Consider the priority of settings, should be Local > Global > XDG > System (from the comment of GfW issue #316)

Then, in my test, TortoiseGit always saves config to XDG only, and read it back from Global. This leads to the effective setting is never changed.