Programmatically check if HEAD is detached?

Question

I want to know whether I'm in a "HEAD detached" state in a script.

Currently I parse the output of git status but I dislike doing so because I've heard that it's a bad practice to parse Git output that's meant for human - I want a program-friendly interface to tell me whether HEAD is detached. I also don't want to manually look into .git/HEAD or parse git description or git branch.

Any ideas?

See https://stackoverflow.com/questions/6976473/what-does-the-term-porcelain-mean-in-git — Lasse V. Karlsen, Sep 07 '18 at 11:38
You can try `git rev-parse --symbolic-full-name HEAD`, if it outputs HEAD, you're in detached mode, if it outputs a branch name, you're on that branch. — Lasse V. Karlsen, Sep 07 '18 at 11:41
`git rev-parse --abbrev-ref HEAD` will give you a branch name if you're on a branch else will give you the detached HEAD hash — clamentjohn, Sep 07 '18 at 12:07

score 18 · Accepted Answer · answered Sep 07 '18 at 12:07

18

The easiest command is probably:

$ git symbolic-ref -q HEAD

and check the exit status: 0 means normal; 1 is detached.

From the docs of git-symbolic-ref:

-q, --quiet
   Do not issue an error message if the <name> is not a symbolic ref
   but a detached HEAD; instead exit with non-zero status silently.

answered Sep 07 '18 at 12:07

rodrigo

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Great solution. I'll just take this one. – iBug Sep 08 '18 at 03:21

Masoud · Answer 2 · 2018-09-07T12:00:29.183

8

Programmatically you need to a wrapper for Git protocol.

For example, by GitPython you're able to find out the repo detached or not repo.head.is_detached

edited Sep 07 '18 at 12:00

answered Sep 07 '18 at 11:35

Masoud

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I didn't mention what language I'm programming in. It could be Bash where the only interface is the `git` binary. And that's good - Once you know how to do it in Bash you can do it in any language - by calling `git` binary. – iBug Sep 07 '18 at 11:37
@iBug `git symbolic-ref HEAD` may help you and just indicate the fatal error by `grep` command. – Masoud Sep 07 '18 at 12:03

score 1 · Answer 3 · answered Nov 28 '20 at 14:40

1

Use git branch to find a detached HEAD...

$ git branch -q
* (HEAD detached at c61a6d2)
  master

answered Nov 28 '20 at 14:40

Mike Pennington

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Are you sure this output is ready for consumption (i.e. text parsing)? – iBug Nov 28 '20 at 16:11
Sure enough to use it in [my git wrapper](https://github.com/mpenning/git_crazy/blob/63a32ad5a525c2113ab7e0434b8bc8acfdb1c356/gitc.py#L1618). Could git change output? Yes, but vulnerabiity to bit-rot is common to any code you write. If you're worried, write a unit test... – Mike Pennington Nov 28 '20 at 16:15

score 1 · Answer 4 · answered Mar 14 '22 at 10:34

1

From git 2.22, you can also use:

git branch --show-current

This prints nothing when not on a branch.

answered Mar 14 '22 at 10:34

ak2

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Programmatically check if HEAD is detached?

4 Answers4