```shell
git clone ... && cd ...
git remote remove origin
# move directory to root, remove all other from history
git filter-branch --prune-empty --subdirectory-filter DIRECTORY master
# move directory with history rewrite
git filter-branch -f --index-filter \
  'git ls-files -s | sed "s-\t\"*-&DIRECTORY/-" |
  GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
  git update-index --index-info &&
  mv "$GIT_INDEX_FILE.new" "$GIT_INDEX_FILE"' HEAD
```