Kevin Reid's blog

Let's say you have two or more independent Git branches, and you want to make sure the combination of them works correctly, but aren't ready to permanently merge or rebase them together. You can do a merge and discard it (either by resetting afterward or using a temporary branch), but that takes extra commands when you're done with the trial. Here's the script I put together to eliminate all unnecessary steps:

#!/bin/sh
set -e
set -x
git checkout --detach HEAD
git merge --no-edit -- "$@"

In a single command, this merges HEAD and any branches given as arguments and leaves you at the merge as a detached HEAD. This means that when you're done with it you can just switch back to your branch (git checkout - is a shortcut for that) and the merge is forgotten. If you committed changes on top of the merge, git checkout will tell you about them and you can transplant them to a real branch with git cherry-pick.