What is a ‘detached HEAD’ state in Git?

Understanding the ‘detached HEAD’ state requires a fundamental understanding of how Git works. Git is a distributed version control system that allows you to manage your project’s history or, in other words, to keep track of your code changes over time. In Git, the term ‘HEAD’ is a reference to the current snapshot of your project. In a typical Git scenario, the ‘HEAD’ points to the latest commit on the currently checked out branch.

However, there are scenarios where your ‘HEAD’ might not point to the latest commit on the current branch. This state is what is known as a ‘detached HEAD’ state.

What is a Detached HEAD?

A detached HEAD in Git means that the ‘HEAD’ pointer is not pointing to the latest commit of the current branch but to a specific commit in the repository’s history. In other words, you have checked out a commit that is not the latest commit in the branch. This scenario often happens when you check out an older commit or a commit hash instead of a branch.

What Happens in a Detached HEAD State?

When in a detached HEAD state, you can browse the code, make changes, and even commit those changes. But these changes won’t be associated with any branch. As soon as you switch back to a branch, any commits made in this state will be lost unless saved to a new branch.

How to Get into a Detached HEAD State?

You can enter a detached HEAD state by checking out an older commit or a commit hash, like so:

git checkout <commit-hash>

How to Exit from a Detached HEAD State?

To exit from a detached HEAD state, you need to check out a branch. If you’ve made changes that you want to keep, you should create a new branch while still in the detached HEAD state:

git checkout -b <new-branch-name>

This command will create a new branch named <new-branch-name> and set it to point to the commit you’re currently on (the commit that HEAD is pointing to).

If you want to discard the changes, you can simply check out the branch you were on before entering the detached HEAD state:

git checkout <existing-branch-name>

In conclusion, the detached HEAD state is a temporary state in Git that lets you navigate around your project’s history, but you should be careful not to lose changes by forgetting to create a new branch if necessary.