Normalize the paths of all files, avoiding duplicate misses of directories


For example with [Products.PloneHelpCenter](https://github.com/collective/Products.PloneHelpCenter) I get this report, where in all cases the directories are there and have a file in them:

missing from VCS:
  Products/PloneHelpCenter/profiles/default/workflows/helpcenter_workflow/
  Products/PloneHelpCenter/profiles/default/workflows/helpcenterfolder_workflow/
  Products/PloneHelpCenter/profiles/default/workflows/helpcentersubitem_workflow/
missing from sdist:
  Products/PloneHelpCenter/profiles/default/workflows/helpcenter_workflow
  Products/PloneHelpCenter/profiles/default/workflows/helpcenterfolder_workflow
  Products/PloneHelpCenter/profiles/default/workflows/helpcentersubitem_workflow