Merge two remote branches in a Git repository

If you have remote-tracking branches set up locally, it's as simple as:

git checkout production
git merge development
git push origin production

If you have not yet set up remote-tracking branches, you could do something like:

git fetch origin
git checkout production     # or `git checkout -b production origin/production` if you haven't set up production branch locally
git merge origin/development
git push origin production