Merging by rebase

This can only be done by repo collaborators. If you use the github "merge" button, a merge commit will always be created, even if the merge was fast-forward.

git checkout master
git pull upstream master
git rebase master feature_branch  # will leave you in feature_branch
git checkout master
git merge feature_branch  # will not create a merge commit!
git push upstream master

How to fix messed history

Sometimes whenever one perform a rebase, the history is messed on the github pull request and includes many unrelated commits. The following procedure should allow to clean the history and keep only the relevant commits.

git checkout master
git fetch upstream
git rebase upstream/master
git checkout new-branch
git rebase master
git log # Check that it has worked as expected
git push -f 

Check out pull requests to your local repo

https://gist.github.com/3342247

Find & replace in the whole repo

git ls-files | xargs sed -i -e 's/old-method-name/new-method-name/g'