fix: make GITHUB_REF env var optional

[billputer]

Fixes #80

Certain workflows don't set a GITHUB_REF variable, because the triggering event doesn't have a branch or tag, so this PR makes GITHUB_REF optional. This changes the ordering of tags in tests since the Branch tag is now added at the end. It also adds two tests to validate this behavior, although I'm not convinced they provide much value.

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[billputer]

I've updated this to fix conflicts introduced in #92.

Interestingly enough, although #92 allows skipping setting session tags, the code still requires that the associated environment variables are set. It might be worth splitting that functionality out into a separate function.

[allisaurus]

Thanks a lot @billputer ! Code LGTM. Can you provide some test output or guidance on which workflows may trigger the original issue? I tried to reproduce by setting a status but no dice.

[billputer]

Thanks a lot @billputer ! Code LGTM. Can you provide some test output or guidance on which workflows may trigger the original issue? I tried to reproduce by setting a status but no dice.

I'm specifically using the "deployment" webhook event. An external system creates a Deployment in GitHub which triggers our workflow. Here's a truncated version:

name: deploy
on: ['deployment']

jobs:
  deploy:
    runs-on: ubuntu-18.04
    steps:
    - name: Configure AWS Credentials
      uses: aws-actions/configure-aws-credentials@v1
      with:
        aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
        aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
        aws-region: us-west-2
    # ...rest of deploy code

If you're interested in triggering that, here's roughly how we've been creating a GitHub Deployment in testing.

npm install @octokit/rest
export GITHUB_TOKEN=<github_token_here>
node

const { Octokit } = require("@octokit/rest");
const octokit = new Octokit({
  auth: process.env.GITHUB_TOKEN,
  userAgent: 'deploy testing',
})

octokit.repos.createDeployment({
  owner: "billputer",
  repo: "deploy-testing",
  ref: "4cd8eff6e93378175f2d204ef5235cf2271d59d3",
  description: "Deploy triggered by Bill via CLI",
  environment: "testing",
  task: "deploy",
  payload: {},
  required_contexts: [],
  auto_merge: false,
}).then(data => { console.log(data) });

The key here is that the "ref" is a commit sha. If you instead pass a ref of "master", the GITHUB_REF environment variable is set.

Let me know if that's helpful, or if you need any additional context.