How did I end up with a detached HEAD?

Question

I checked out a commit/branch from master, and then checked out back to master and wrote something. After that, I committed it, but I ended up with a detached HEAD. Why?

Answer 1

For recovering a detached-HEAD, you can :

git checkout master

Answer 2

Problem and solution

Close inspection of the IntelliJ-IDEA log reveals the nature of the problem. After creating your first two commits, you were in the following situation:

Somehow, you checked out your first commit, which put you in detached-HEAD state:

Then, similarly, you checked out your second commit (which happened to be the tip of your master branch). This still left you in detached-HEAD state:

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You write:

I checked out a commit/branch from master [...]

Be careful. Checking out a commit that happens to be the tip of a branch is not equivalent to checking out that branch!

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Note that HEAD is now pointing directly to a commit, not to a branch. That is the definition of "detached HEAD". The fact that HEAD points to the same commit as master changes nothing about the fact that your HEAD is detached.

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Some IDEs may not give you a clear indication that you are in fact in detached-HEAD state. Even git log --decorate, for a long time, gave you no clue as to whether HEAD was pointing to master, or detached and pointing directly at master's tip.

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You then made a third commit, which, as expected, still left you with a detached HEAD; your master branch still points to the second commit.

To get out of detached HEAD-state, you need to reattach HEAD to a branch (master, here). How depends on what you want to do. In the following, I'm assuming you have access to the Git CLI:

• If you want to discard your third commit, simply run

  git checkout master
  

  and you'll end up back in this situation:

• If you want to keep your third commit and make master point to it, run

  git branch -f master HEAD
  

  and then

   git checkout master
  

Parting tip

Learning Git in an IDE is a recipe for disaster. I recommend you build your understanding at the command line first, and only then start using Git from within a GUI, if you feel that doing so would improve your workflow.