gistfile1.sh

git clone https://github.com/reactphp/react source
cd source

# list all branches that should be preserved
# only version branches listed, as to skip WIP branches
git branch 0.3 origin/0.3
git branch 0.4 origin/0.4
#master is already included (default from clone)

# remove reference from origin to speed up rewriting its references
git remote remove origin

# now rewrite the whole history by moving src/React/* to src/*
# this will allow us to extract the contents in a consistent directory structure
git filter-branch --index-filter \
                    'git ls-files -s | sed "s/src\/React/src/" |
                            GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
                                    git update-index --index-info &&
                     mv "$GIT_INDEX_FILE.new" "$GIT_INDEX_FILE"' -- --all

# remove backup references automatically created by git-filter-branch
rm -r .git/refs/original/

# now that everything is always located in src/$COMPONENT we can easily extract its sole history
git filter-branch --subdirectory-filter src/EventLoop/ -- --all

# remove backup references automatically created by git-filter-branch
rm -r .git/refs/original/

# Done already! :)

# Final steps:
#  gitg # inspect repo locally, then consider pushing:
#  git push --all https://github.com/reactphp/event-loop # push all branches to target repo
#  git push --tags https://github.com/reactphp/event-loop # push all tags to target repo