How to copy commits from one Git repo to another?

Clone basic repo

git clone https://github.com/user1/project1
cd project1

Add external repo

git remote add oldrepo https://github.com/user1/project2

Get the old repo commits

git remote update

examine the whole tree

git log --all --oneline --graph --decorate

Copy (cherry-pick) the commits from the old repo into your new local one

git cherry-pick sha-of-commit-one
git cherry-pick sha-of-commit-two
git cherry-pick sha-of-commit-three

check your local repo is correct

git log

send your new tree (repo state) to github

git push origin master

remove the now-unneeded reference to oldrepo

git remote remove oldrepo