I have a custom ImageManipulation library that is based on a particular external library. (This is on master branch.) Right now, I want to test how another library would work, so I would do:

```
git checkout -b experiment_new_library

```

If then, I decide this works fine, and I merge it into master, what would be the good approach in order to be able to have ‘saved’ somehow that old master branch with the old Image library? How should you save that state in case you want to rollback to it?