go文件和目录复制，文件复制是建立硬链接，如失败，则复制文件内容

go-copy-file-and-dir

// CopyFile copies a file from src to dst. If src and dst files exist, and are
// the same, then return success. Otherise, attempt to create a hard link
// between the two files. If that fail, copy the file contents from src to dst.
func CopyFile(src, dst string) (err error) {
	sfi, err := os.Stat(src)
	if err != nil {
		return
	}
	if !sfi.Mode().IsRegular() {
		// cannot copy non-regular files (e.g., directories,
		// symlinks, devices, etc.)
		glog.Errorf("CopyFile: non-regular source file %s (%q)", sfi.Name(), sfi.Mode().String())
	}
	dfi, err := os.Stat(dst)
	if err != nil {
		if !os.IsNotExist(err) {
			return
		}
	} else {
		if !(dfi.Mode().IsRegular()) {
			glog.Errorf("CopyFile: non-regular destination file %s (%q)", dfi.Name(), dfi.Mode().String())
		}
		if os.SameFile(sfi, dfi) {
			return
		}
	}
	if err = os.Link(src, dst); err == nil {
		return
	}
	err = copyFileContents(src, dst)
	return
}

// copyFileContents copies the contents of the file named src to the file named
// by dst. The file will be created if it does not already exist. If the
// destination file exists, all it's contents will be replaced by the contents
// of the source file.
func copyFileContents(src, dst string) (err error) {
	in, err := os.Open(src)
	if err != nil {
		return
	}
	defer in.Close()
	out, err := os.Create(dst)
	if err != nil {
		return
	}
	defer func() {
		cerr := out.Close()
		if err == nil {
			err = cerr
		}
	}()
	if _, err = io.Copy(out, in); err != nil {
		return
	}
	err = out.Sync()
	return
}
func CopyDir(source string, dest string) (err error) {

	// get properties of source dir
	sourceinfo, err := os.Stat(source)
	if err != nil {
		return err
	}
	// create dest dir
	err = os.MkdirAll(dest, sourceinfo.Mode())
	if err != nil {
		return err
	}
	directory, _ := os.Open(source)
	objects, err := directory.Readdir(-1)
	for _, obj := range objects {
		sourcefilepointer := source + "/" + obj.Name()
		destinationfilepointer := dest + "/" + obj.Name()
		if obj.IsDir() {
			// create sub-directories - recursively
			err = CopyDir(sourcefilepointer, destinationfilepointer)
			if err != nil {
				glog.Infof("Copy dir err: %v", err)
			}
		} else {
			// perform copy
			err = CopyFile(sourcefilepointer, destinationfilepointer)
			if err != nil {
				glog.Infof("Copy dir err: %v", err)
			}
		}
	}
	return
}