Show git branch name OR commit id

Question

I am trying to reproduce the behavior of my shell prompt when it comes to showing the current branch name. I'm here using fish but most shell have this feature.

If I use the command

git rev-parse --abbrev-ref --verify HEAD

it returns me

master

Good!

Now, if I checkout an old commit, my prompt shows

And if I run the command above again it returns

HEAD

Which is not what I want. I want 3171f5a just like the prompt. So I've got a new command.

git rev-parse --short --verify HEAD

3171f5a

Nice! But if I come back to master it gives me

617ca76

Do you know if there's a command to give me that output straight away, without an if statement checking if the return value is HEAD. (shorten hash or not is fine)

Thank you very much

Answer 1

The one-line way to do this in the shell is to use two separate Git commands:

git symbolic-ref --short -q HEAD || git rev-parse --short HEAD

In the detached HEAD case, the git symbolic-ref command fails (while the -q prevents it from complaining to stderr) and the second git rev-parse command goes on to print the shortened hash ID.

Note that when you are on an unborn branch, the git symbolic-ref command succeeds and you get the (shortened) name of the unborn branch.