Function isAbs

cli/command/container/cp.go:526–528

IsAbs is a platform-agnostic wrapper for filepath.IsAbs. On Windows, golang filepath.IsAbs does not consider a path \windows\system32 as absolute as it doesn't start with a drive-letter/colon combination. However, in docker we need to verify things such as WORKDIR /windows/system32 in a Dockerfile

(path string)

// by the daemon). This SHOULD be treated as absolute from a docker processing
// perspective.
func isAbs(path string) bool {
	return filepath.IsAbs(path) || strings.HasPrefix(path, string(os.PathSeparator))
}