How to remove deleted branch names from Git autocomplete

This is actually just a kind of short-cut to this SO. But if you want to skip the reading then here is the one-liner which does the cleaning for you.

git fetch --prune --all

Also to prune all local branches which have already been merged:

git branch -d $(git branch --merged)
git remote prune origin
git branch -d $(git branch | sed '$d')