Update: Installing works with the below but it fails to authenticate, prompting for a GUI-based URL MFA.

      - name: Install GitHub CLI
        run: |
          URL=https://github.com/cli/cli/releases/download/v0.11.1/gh_0.11.1_linux_amd64.deb
          TEMP_DIR="$(pwd)"
          TEMP_DEB="$(pwd)/gh_0.11.1_linux_amd64.deb"
          wget -O "$TEMP_DEB" "$URL"
          ls -la $TEMP_DIR
          sudo apt install "$TEMP_DEB"
          rm -f "$TEMP_DEB"

Failure log:

Run echo "Checking out from PR URL: https://api.github.com/repos/slalom-ggp/dataops-infra/pulls/122"
Checking out from PR URL: https://api.github.com/repos/slalom-ggp/dataops-infra/pulls/122
Notice: authentication required
Press Enter to open github.com in your browser... /usr/bin/xdg-open: 851: /usr/bin/xdg-open: www-browser: not found
/usr/bin/xdg-open: 851: /usr/bin/xdg-open: links2: not found
/usr/bin/xdg-open: 851: /usr/bin/xdg-open: elinks: not found
/usr/bin/xdg-open: 851: /usr/bin/xdg-open: links: not found
/usr/bin/xdg-open: 851: /usr/bin/xdg-open: lynx: not found
/usr/bin/xdg-open: 851: /usr/bin/xdg-open: w3m: not found
xdg-open: no method available for opening 'https://github.com/login/oauth/authorize?client_id=178c6fc778ccc68e1d6a&redirect_uri=http%3A%2F%2F127.0.0.1%3A33511%2Fcallback&scope=repo+read%3Aorg+gist&state=2f9d7df6cfbb09aefbf7'
error opening web browser: exit status 3
Please open the following URL manually:
https://github.com/login/oauth/authorize?client_id=178c6fc778ccc68e1d6a&redirect_uri=http%3A%2F%2F127.0.0.1%3A33511%2Fcallback&scope=repo+read%3Aorg+gist&state=2f9d7df6cfbb09aefbf7
If you are on a server or other headless system, use this workaround instead:
  1. Complete authentication on a GUI system;
  2. Copy the contents of `~/.config/gh/hosts.yml` to this system.

Any plans to do something like https://github.com/marketplace/actions/setup-hub?

@aaronsteers GitHub CLI is pre-installed in Actions runners. To use it:

- uses: actions/checkout@v2

- name: GitHub CLI example
  run: gh issue list
  env:
    GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}

I understand that this has to be better documented; I'll add a label as a TODO item for us. Thanks for your ask!

@mislav - Awesome. That's a big help.