prow/cmd/deck/pr_history.go
func getPullCommitHash(pull string) (string, error) {
	match := pullCommitRe.FindStringSubmatch(pull)
	if len(match) != 2 {
		expected := "branch:hash,pullNumber:hash"
		return "", fmt.Errorf("unable to parse pull %q (expected %q)", pull, expected)
	}
	return match[1], nil
}
func getPullCommitHash(pull string) (string, error) {
	match := pullCommitRe.FindStringSubmatch(pull)
	if len(match) != 2 {
		expected := "branch:hash,pullNumber:hash"
		return "", fmt.Errorf("unable to parse pull %q (expected %q)", pull, expected)
	}
	return match[1], nil
}
// gets the pull commit hash from metadata