Fix branch name detection for GitHub Actions CI (#111)

* Fix typo (it is 'refs/heads/' not 'refs/head')

* Detect GITHUB_HEAD_REF='' as falsey

Author: LocoDelAssembly

lib/codecov.rb

@@ -192,9 +192,13 @@ def build_params(ci)
     when GITHUB
       # https://help.github.com/en/actions/configuring-and-managing-workflows/using-environment-variables#default-environment-variables
       params[:service] = 'github-actions'
-      params[:branch] = ENV['GITHUB_HEAD_REF'] || ENV['GITHUB_REF'].sub('refs/head/', '')
-      # PR refs are in the format: refs/pull/7/merge for pull_request events
-      params[:pr] = ENV['GITHUB_REF'].split('/')[2] unless ENV['GITHUB_HEAD_REF'].nil? || ENV['GITHUB_HEAD_REF'].empty?
+      if (ENV['GITHUB_HEAD_REF'] || '').empty?
+        params[:branch] = ENV['GITHUB_REF'].sub('refs/heads/', '')
+      else
+        params[:branch] = ENV['GITHUB_HEAD_REF']
+        # PR refs are in the format: refs/pull/7/merge for pull_request events
+        params[:pr] = ENV['GITHUB_REF'].split('/')[2]
+      end
       params[:slug] = ENV['GITHUB_REPOSITORY']
       params[:build] = ENV['GITHUB_RUN_ID']
       params[:commit] = ENV['GITHUB_SHA']

test/test_codecov.rb

@@ -484,8 +484,8 @@ def test_github_pull_request
   def test_github_push
     ENV['CI'] = 'true'
     ENV['GITHUB_ACTIONS'] = 'true'
-    ENV['GITHUB_HEAD_REF'] = nil
-    ENV['GITHUB_REF'] = 'refs/head/master'
+    ENV['GITHUB_HEAD_REF'] = ''
+    ENV['GITHUB_REF'] = 'refs/heads/master'
     ENV['GITHUB_REPOSITORY'] = 'codecov/ci-repo'
     ENV['GITHUB_RUN_ID'] = '1'
     ENV['GITHUB_SHA'] = 'c739768fcac68144a3a6d82305b9c4106934d31a'