Getting current branch and commit hash in GitHub action

Question

I want to build a docker image using a GitHub action, migrating from TeamCity.

In the build script, I want to tag the image with a combination of branch and commit, e.g. master.ad959de. Testing that locally, I get that information like this:

git_branch=`git symbolic-ref --short HEAD`
git_hash=`git rev-parse --short HEAD`
docker_version=${git_branch}.${git_hash}

This is the relevant part of the GitHub action:

name: CI
on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v1

    - name: Create docker image
      run: ./docker-build.sh  

Running that script in that GitHub action results in this error:

fatal: ref HEAD is not a symbolic ref

How can I generate a tag like that inside a GitHub action?

Answer 1

from Using environment variables

github provides two variables that are useful here, you'll need to process them a bit to get the values you desire:

GITHUB_SHA: The commit SHA that triggered the workflow. For example, ffac537e6cbbf934b08745a378932722df287a53.

GITHUB_REF: The branch or tag ref that triggered the workflow. For example, refs/heads/feature-branch-1. If neither a branch or tag is available for the event type, the variable will not exist.

The short values can be extracted like this:

git_hash=$(git rev-parse --short "$GITHUB_SHA")
git_branch=${GITHUB_REF#refs/heads/}