Add branch detection for more CI providers (#189)

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## HEAD
 
+- Add support for GitHub Actions env vars (https://github.com/heroku/hatchet/pull/189)
+
 ## 7.4.0
 
 - Supports "basic" scaledown (https://github.com/heroku/hatchet/pull/193)

lib/hatchet.rb

@@ -26,6 +26,15 @@ module Hatchet
   Runner  = Hatchet::GitApp
 
   def self.git_branch
+    # https://circleci.com/docs/variables
+    return ENV['CIRCLE_BRANCH'] if ENV['CIRCLE_BRANCH']
+    # https://docs.github.com/en/actions/learn-github-actions/environment-variables
+    # GITHUB_HEAD_REF is provided for PRs, but blank for branch actions.
+    return ENV['GITHUB_HEAD_REF'] if !ENV['GITHUB_HEAD_REF'].empty?
+    # GITHUB_REF_NAME is incorrect on PRs (`1371/merge`), but correct for branch actions.
+    return ENV['GITHUB_REF_NAME'] if ENV['GITHUB_REF_NAME']
+    # https://devcenter.heroku.com/articles/heroku-ci#immutable-environment-variables
+    return ENV['HEROKU_TEST_RUN_BRANCH'] if ENV['HEROKU_TEST_RUN_BRANCH']
     # TRAVIS_BRANCH works fine unless the build is a pull-request. In that case, it will contain the target branch
     # not the actual pull-request branch! TRAVIS_PULL_REQUEST_BRANCH contains the correct branch but will be empty
     # for push builds. See: https://docs.travis-ci.com/user/environment-variables/

lib/hatchet/app.rb

@@ -11,7 +11,7 @@ class App
         "https://github.com/heroku/heroku-buildpack-ruby.git"
       }
     }
-    HATCHET_BUILDPACK_BRANCH = -> { ENV['HATCHET_BUILDPACK_BRANCH'] || ENV['HEROKU_TEST_RUN_BRANCH'] || Hatchet.git_branch }
+    HATCHET_BUILDPACK_BRANCH = -> { ENV['HATCHET_BUILDPACK_BRANCH'] || Hatchet.git_branch }
 
     attr_reader :name, :stack, :repo_name, :app_config, :buildpacks, :reaper, :max_retries_count