SHELL

git replace master with branch

git checkout better_branch
git merge --strategy=ours --no-commit master
git commit -m "Replacing master branch with better_branch"
git checkout master
git merge better_branch
git push origin master

replace master branch entirely with another branch

git branch -m master old-master
git branch -m seotweaks master
git push -f origin master

Git replace master branch, entirely, from another branch

git checkout new_branch
git merge -s ours master
git checkout master
git merge new_branch