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?

Here is what I did:

1. Create a new project and create git repository.
2. git add
3. git commit
4. type some words
5. git commit
6. checkout to previous commit

7. checkout back

8. type some word

9. try to commit; it prompts there is a detached head.

IntelliJ IDEA's console shows:

17:08:58.143: cd C:\Users\jiahao\IdeaProjects\testtt\src
17:08:58.143: git init
Initialized empty Git repository in C:/Users/jiahao/IdeaProjects/testtt/src/.git/
17:09:16.331: cd C:\Users\jiahao\IdeaProjects\testtt\src
17:09:16.331: git -c core.quotepath=false add --ignore-errors -- C.java
17:09:24.407: cd C:\Users\jiahao\IdeaProjects\testtt\src
17:09:24.407: git -c core.quotepath=false commit --only -F C:\Users\jiahao\AppData\Local\Temp\git-commit-msg-0.txt -- C.java
[master (root-commit) 22d1c79] first commit
 1 file changed, 6 insertions(+)
 create mode 100644 C.java

17:09:38.060: cd C:\Users\jiahao\IdeaProjects\testtt\src
17:09:38.060: git -c core.quotepath=false commit --only -F C:\Users\jiahao\AppData\Local\Temp\git-commit-msg-0.txt -- C.java
[master 69084f3] second commit
 1 file changed, 1 insertion(+)

17:09:44.136: cd C:\Users\jiahao\IdeaProjects\testtt\src
17:09:44.136: git -c core.quotepath=false checkout 22d1c7919eab50925411d9bbb8a9ad1575608c27
Note: checking out '22d1c7919eab50925411d9bbb8a9ad1575608c27'.
You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.
If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:
  git checkout -b <new-branch-name>
HEAD is now at 22d1c79... first commit
17:09:46.576: cd C:\Users\jiahao\IdeaProjects\testtt\src
17:09:46.576: git -c core.quotepath=false checkout 69084f344b79a48da92855d3fb633a28a672a302
Previous HEAD position was 22d1c79... first commit
HEAD is now at 69084f3... second commit
17:18:26.999: cd C:\Users\jiahao\IdeaProjects\testtt\src
17:18:26.999: git -c core.quotepath=false commit --only -F         C:\Users\jiahao\AppData\Local\Temp\git-commit-msg-0.txt -- C.java
[detached HEAD 783fbf2] third commit
1 file changed, 1 insertion(+)

Viddah

I suspect you didn't just checkout back to master. It would help if you could give a complete example (from git init onwards) of an exact set of steps to reproduce the problem. – Stinson

No, that's not an exact set of steps - "checkout back" doesn't tell us exactly what you did. Ideally, do this from the command line to make it clearer than from an IDE. – Stinson

Also show the results of git status from the command line. – Stinson

Can you give us the lines in git reflog that are relevant? – Jackpot

When I use command line, trying to reproduce the problem, I fail because it works! So I think maybe it's IntelliJ IDEA's BUG. I will show you the reflog in IntelliJ IDEA later. Thanks. – Viddah

Whatever you did in IntelliJ ("checkout to previous commit") caused commands of the form git checkout <commit-sha> to be run, as shown by the log. Such a command checks out a commit rather than a branch, which puts you in detached-HEAD state. – Christo

Yes when I checkout to previous commit it will put me in detached-HEAD state, but after that I checkout to master, and , in my opinion, I will not be in detached-HEAD state anymore. Am I wrong? However, the fact is that after I checkout to master, I am still in detached-HEAD state. – Viddah

More info here:stackoverflow.com/questions/34519665/… – Griffy

Answer 1

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:

---

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!

---

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.

---

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.

---

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.

Christo

"Be careful. Checking out a commit that happens to be the tip of a branch is not equivalent to checking out that branch!" ... delivered a real moment of clarity for my 60yo brain there! I'm just learning, but have to say I've found the intellij UI helpful in that I have at least got started with making some use of Git, after several attempts at doing that via the CLI. Was always baffled by the complexity vs the minimal rewards you see as a solo dev. – Frightened

Answer 2

I accidentally ran into detached-HEAD while developing a Java Spring project using IntelliJ 2020.2. This is how i got back to normal.

In git tool window [Alt+9], branch "Log: origin/master", had 3 labels: yellow = HEAD, green = master, violet = origin/master:

'HEAD' and 'origin/master' were applied to the latest commit 'master' was applied to an earlier commit .

To get out of detached-head and reset it to the desired state 'HEAD & master & origin/master all applied to branch's latest commit', right-clicked 'master' node 'Remote' list (located left to the branch's history under Log) and chose 'Checkout'

Such got back to regular state in latest commit in branch

Ergot

Answer 3

For recovering a detached-HEAD, you can :

git checkout master

Locule

This does not fix the current branch – Tilford