Rebase PR on top of master and merge --ff-only. a.k.a. No GitHub, I do not want unreadable git history due to merges.

gistfile1.txt

# Merge GitHub pull request on top of the `master` branch
mpr = "!f() { \
    if [ $(printf \"%s\" \"$1\" | grep '^[0-9]\\+$' > /dev/null; printf $?) -eq 0 ]; then \
        git fetch origin refs/pull/$1/head:pr/$1 && \
        git rebase master pr/$1 && \
        git checkout master && \
        git merge --ff-only pr/$1 && \
        git branch -D pr/$1; \
    fi \
}; f"