What is `git checkout --orphan` used for?

Question

I've just discovered git checkout --orphan, but I don't know how to use it. Its help page says it creates a new unparented branch.

In the master branch, I've tried git checkout --orphan br, only to see the files in the working directory change to “Changes to be committed”, and the git log saying fatal: bad default revision 'HEAD'.

So what's the advantage of using git checkout --orphan?

Solution 1

The core use for git checkout --orphan is to create a branch in a git init-like state on a non-new repository.

Without this ability, all of your git branches would have a common ancestor, your initial commit. This is a common case, but in no way the only one. For example, git allows you to track multiple independent projects as different branches in a single repository.

That's why your files are being reported as “changes to be committed”: in a git init state, the first commit isn't created yet, so all files are new to git.

Solution 2

It's used by e.g. GitHub Pages, which stores a repo's website inside the repo but on a separate branch. There's no reason to store anything but the website's history on this branch.

Solution 3

We were moving to a public repo from a private one and because of sensitive commit information, we wanted to reset a branch as new and push it as a blank branch. Here is a typical way of a workflow for that:

how to delete all commit history in github?