Extract part of a Git repository while keeping the history

extract_sub_repo.sh

# create a list of files to NOT keep
create_black_list > blacklist

# add old files which have been renamed
for f in $(cat blacklist); do
    git log --pretty=oneline --follow --name-only $f | grep -v ' ' | sort -u >> blacklist
done

# remove files and commits from the Git history (may take a while...)
for f in $(cat blacklist); do
    echo $f
    git filter-branch --index-filter "git rm -f --cached --ignore-unmatch $f" -f --prune-empty 
done

# clone the repo to remove old git references and shrink it considerably
git clone file:///path/to/repo new_repo