How to make sub-branch the master branch?

Question

I've seen this answer, but I'm unsure of what the answerer meant by using git branch -f .. in order to complete the task.

I have three branches, my master branch has a bunch of files that I don't want sticking around, which I know they will if I use merge. I somewhat understand deleting a branch, but can I really do that to the master branch?

I know there is a probably simple solution to the problem, but could someone explain what each git command is doing? It would help a fair bit.

Question: How can I merge my sub-branch into the master while only keeping the files from the sub-branch and none from the master whilst keeping my sub-branch?

Answer 1

You can checkout the sub-branch, delete master branch, checkout a copy of your sub-branch and name it master.

git checkout sub-branch
git branch -D master
git checkout -b master