prow/github/client.go
func (c *Client) GetFile(org, repo, filepath, commit string) ([]byte, error) {
	c.log("GetFile", org, repo, filepath, commit)

	url := fmt.Sprintf("/repos/%s/%s/contents/%s", org, repo, filepath)
	if commit != "" {
		url = fmt.Sprintf("%s?ref=%s", url, commit)
	}

	var res Content
	code, err := c.request(&request{
		method:    http.MethodGet,
		path:      url,
		exitCodes: []int{200, 404},
	}, &res)

	if err != nil {
		return nil, err
	}

	if code == 404 {
		return nil, &FileNotFound{
			org:    org,
			repo:   repo,
			path:   filepath,
			commit: commit,
		}
	}

	decoded, err := base64.StdEncoding.DecodeString(res.Content)
	if err != nil {
		return nil, fmt.Errorf("error decoding %s : %v", res.Content, err)
	}

	return decoded, nil
}
func (c *Client) GetFile(org, repo, filepath, commit string) ([]byte, error) {
	c.log("GetFile", org, repo, filepath, commit)

	url := fmt.Sprintf("/repos/%s/%s/contents/%s", org, repo, filepath)
	if commit != "" {
		url = fmt.Sprintf("%s?ref=%s", url, commit)
	}

	var res Content
	code, err := c.request(&request{
		method:    http.MethodGet,
		path:      url,
		exitCodes: []int{200, 404},
	}, &res)

	if err != nil {
		return nil, err
	}

	if code == 404 {
		return nil, &FileNotFound{
			org:    org,
			repo:   repo,
			path:   filepath,
			commit: commit,
		}
	}

	decoded, err := base64.StdEncoding.DecodeString(res.Content)
	if err != nil {
		return nil, fmt.Errorf("error decoding %s : %v", res.Content, err)
	}

	return decoded, nil
}
// GetFile uses GitHub repo contents API to retrieve the content of a file with commit SHA.
// If commit is empty, it will grab content from repo's default branch, usually master.
// TODO(krzyzacy): Support retrieve a directory
//
// See https://developer.github.com/v3/repos/contents/#get-contents