title: Git is dropping my .gitignore files at checkout
body: <p>When I checkout branch A to branch B, some files in my .gitignore A are dropped if they're not in in .gitignore branch B.
  I tried to edit my .git/info/exclude file, but I don't see the difference.
  I tried with --assume-unchanged and --skip-worktree (keeping the files in .gitignore + make add -f) but I can't checkout if my file is modified. I really need to ignore my file ...
  Have you got some tips to share ?</p>
  
  <p>Thanks</p>