[BUG (or misfeature?)] git checkout and symlinks

  if in a branch [branch1] you track the file: dir1/file1.c
and in the branch [branch2] you track elsewhere/file1.c and dir1 be
symlink on elsewhere, then it's not possible to checkout the branch
[branch1] if your previous checkout was [branch2]. You have to manually
remove the symlink `dir1` else git complains that checkouting branch1
would overwrite dir1/file1.c.

  I'm not sure how to fix this, and it's quite painful actually :)