git checkout

If we want to look at a certain point in history without changing our commit history, we can use git checkout.

git checkout <hash> will jump to that commit and the state of repo at that time. It does not delete commits from your history, it places you at that exact point in your history.

To demonstrate, lets go back to the commit where we first added the hello_world.txt file.

$ git checkout 06ba36d96e1f1dcf905fd442ddd8d6546379178a

First you'll notice that git provides a big warning about this. It wants you to be aware that you are no longer on the HEAD commit. So committing at this point won't affect your history. git status also warns us that we are in a HEAD detached at <hash> state.

Looking at the files in the directory with ls we see only two files, both empty, since we hadn't added text yet to them.

To return to the top of our project and be able to continue editing our project, use git checkout master. master is the name of our branch. Don't worry about that now, as we'll cover branching in a bit.

$ git checkout master

We're back to the most recent commit and can continue making changes again.

Discard Changes

Let's edit our hello_world.txt again. Let's add "some changes".

If we git status, we'll see that hello_world.txt has been modified and is not staged for commit (hasn't been git added yet.)

You'll also see that git has given us some helpful text, recommending we use git add to stage it or git checkout -- <file> to discard the changes.

git checkout -- <file> will undo changes made to the specified <file> that were made after the most recent commit. It will remove them from the working directory.

If we use it on hello_world.txt, the text we just added "some changes" will disappear.

$ git checkout -- hello_world.txt

If we look inside the file, the text is gone.

This can be useful if you've made a lot of changes and don't want to remove them all from your editor manually.