[PATCH 2 of 3] dirstate: walk returns None for files under symlink directory

[Durham Goode]

> I don't understand what "under symlink directory" means. Could you
>explain, please?


If you have a path in your repository like "foo/bar/a" and 'foo' is a
symlink, then 'bar' and 'bar/a' are considered under a symlink directory.
So in the commit messages example:

  mkdir foo && touch foo/a && hg commit -Am "a"
  mv foo bar
  ln -s bar foo


'a' was originally not under a symlink, but then foo became a symlink.
Therefore 'a' is under a symlink directory and should be considered
missing.