<p>How do I add an empty directory (that contains no files) to a Git repository?</p>

You can't.  See the
Git FAQ
.
Currently the design of the git index
  (staging area) only permits files to
  be listed, and nobody competent enough
  to make the change to allow empty
  directories has cared enough about
  this situation to remedy it.
Directories are added automatically
  when adding files inside them. That
  is, directories never have to be added
  to the repository, and are not tracked
  on their own.
You can say "
```
git add <dir>
```
" and it
  will add files in there.
If you really need a directory to
  exist in checkouts you should create a
  file in it. .gitignore works well for
  this purpose; you can leave it empty,
  or fill in the names of files you
  expect to show up in the directory.