Create repository from git subdirectory

git-dir2repo.sh

git clone /XYZ /ABC # To clone your local repository
cd ABC
git remote rm origin
# only rewrite the HEAD branch and ignore tags and other branches
git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter subdirectory_to_repo HEAD 
# then delete the backup reflogs so the space can be truly reclaimed (although now the operation is destructive)
git reset --hard
git for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git update-ref -d
git reflog expire --expire=now --all
git gc --aggressive --prune=now