git add <path> is the same as "git add -A <path>" now, so that
"git add dir/" will notice paths you removed from the directory and
record the removal.
In older versions of Git, "git add <path>" used to ignore removals.
You can say "git add --ignore-removal <path>" to
add only added or modified paths in <path>, if you really want to.
git add -u will operate on the entire tree in Git 2.0 for consistency with "git commit -a" and other commands.
Because there will be no mechanism to make "git add -u" behave as "git add -u .", it is
important for those who are used to "git add -u" (without pathspec) updating the index only for paths in the current subdirectory to start training their fingers to explicitly say "git add -u ." when they mean it before Git 2.0 comes.