Git tracks files, not directories, and we cannot currently add empty directories (The standard trick does not add an empty directory, but instead a file within, see also the FAQ
To setup a test repository with an empty directory, you can use the following script (run it in a temporary directoy).
When checking out, however, the empty directory is ignored. Here too, Git only works with files, not directories, even if the latter are present.
Github and tig display empty directories, gitk does not.
#!/bin/bash
set -e
echo ---- initialize the repo...
#rm -rf .git
git init
echo ---- create an empty tree object...
empty_tree=$(git mktree < /dev/null)
echo ---- create a parent tree containing the empty subtree...
root_tree_ls=$(echo -e 040000 tree $empty_tree\\tvacuum)
root_tree=$(echo "$root_tree_ls" | git mktree)
echo ---- commit...
commit_msg="This commit contains an empty directory"
commit=$(git commit-tree $root_tree -m "$commit_msg")
echo ---- create a branch...
git branch master $commit
# output the ids:
echo ----------------------------------------------------
echo "empty tree:" $empty_tree
echo "root tree: " $root_tree
echo "commit: " $commit