Git: How to squash all commits on branch

Question

I make new branch from master with:

git checkout -b testbranch

I make 20 commits into it.

Now I want to squash those

Answer 1

Based on reading several Stackoverflow questions and answers on squashing, I think this is a good one liner to squash all commits on a branch:

git reset --soft $(git merge-base master YOUR_BRANCH) && git commit -am "YOUR COMMIT MESSAGE" && git rebase -i master

This is assuming master is the base branch.