uniting two git repositories(rough sketch)

fast-export-and-import.sh

cd ~/my_repo1/
git fast-export --all --signed-tags=strip > ~/my_repository.fi

cd ~/my_repo2/
git fast-import < ~/my_repository.fi

# warning: Not updating refs/heads/master (new tip b3e90632cd34e2f4439ba0e6412c2fae3b7929e3
# does not contain b003578907cd0788e350cb3b69e573f59d6db4b8)
# .....

git checkout b3e90632
git checkout -b new_branch
git checkout master
git merge new_branch

git-fetch-and-merge.sh

cd ~/my_repo2/
git remote add repo1 ~/my_repo1/
git fetch repo1
git merge repo1/master

(cd ~/my_repo1/
git fast-export --all --signed-tags=strip ) |

( cd ~/my_repo2/
git fast-import )