Fix CODEBUILD_SOURCE_VERSION matching (#102)

According to AWS CodeBuild User Guide,
CODEBUILD_SOURCE_VERSION depends on the source repository.
When build is triggered by a webhook pull request event,
the value is pull_request number(pr/xxx)
otherwise the value is other than pull request number(commit id, branch name
or tag name).

In the latter case, an error raises like below.

```
/root/caches/vendor/bundle/ruby/2.5.0/gems/codecov-0.2.11/lib/codecov.rb:171
:in `build_params': undefined method `[]' for nil:NilClass (NoMethodError)
```

lib/codecov.rb

@@ -168,7 +168,10 @@ def build_params(ci)
       params[:commit] = ENV['CODEBUILD_RESOLVED_SOURCE_VERSION']
       params[:job] = ENV['CODEBUILD_BUILD_ID']
       params[:slug] = ENV['CODEBUILD_SOURCE_REPO_URL'].match(/.*github.com\/(?<slug>.*).git/)['slug']
-      params[:pr] = ENV['CODEBUILD_SOURCE_VERSION'].match(/pr\/(?<pr>.*)/)['pr'] if ENV['CODEBUILD_SOURCE_VERSION']
+      params[:pr] = if ENV['CODEBUILD_SOURCE_VERSION']
+                      matched = ENV['CODEBUILD_SOURCE_VERSION'].match(%r{pr/(?<pr>.*)})
+                      matched.nil? ? ENV['CODEBUILD_SOURCE_VERSION'] : matched['pr']
+                    end
     when CODESHIP
       # https://www.codeship.io/documentation/continuous-integration/set-environment-variables/
       params[:service] = 'codeship'

test/test_codecov.rb

@@ -639,6 +639,27 @@ def test_codebuild
     assert_equal('f881216b-b5c0-4eb1-8f21-b51887d1d506', result['params']['token'])
   end
 
+  def test_codebuild_source_version_is_other_than_pr_number
+    ENV['CODEBUILD_CI'] = 'true'
+    ENV['CODEBUILD_BUILD_ID'] = 'codebuild-project:458dq3q8-7354-4513-8702-ea7b9c81efb3'
+    ENV['CODEBUILD_RESOLVED_SOURCE_VERSION'] = 'd653b934ed59c1a785cc1cc79d08c9aaa4eba73b'
+    ENV['CODEBUILD_WEBHOOK_HEAD_REF'] = 'refs/heads/master'
+    ENV['CODEBUILD_SOURCE_VERSION'] = 'git-commit-hash-12345'
+    ENV['CODEBUILD_SOURCE_REPO_URL'] = 'https://github.com/owner/repo.git'
+    ENV['CODECOV_TOKEN'] = 'f881216b-b5c0-4eb1-8f21-b51887d1d506'
+
+    result = upload
+
+    assert_equal('codebuild', result['params'][:service])
+    assert_equal('d653b934ed59c1a785cc1cc79d08c9aaa4eba73b', result['params'][:commit])
+    assert_equal('codebuild-project:458dq3q8-7354-4513-8702-ea7b9c81efb3', result['params'][:build])
+    assert_equal('git-commit-hash-12345', result['params'][:pr])
+    assert_equal('owner/repo', result['params'][:slug])
+    assert_equal('master', result['params'][:branch])
+    assert_equal('git-commit-hash-12345', result['params'][:pr])
+    assert_equal('f881216b-b5c0-4eb1-8f21-b51887d1d506', result['params']['token'])
+  end
+
   def test_filenames_are_shortened_correctly
     ENV['CODECOV_TOKEN'] = 'f881216b-b5c0-4eb1-8f21-b51887d1d506'