shallowcopy: copy directory tree with hard link (cp -rpl)

shallowcopy.go

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"time"
)

func usage() {
	fmt.Fprintf(os.Stderr, `shallowcopy: copy directory tree with hard link
Usage: shallowcopy <from> <to>
`)
}

// FIXME: owner mode time acl xattr etc...
func copyinfo(src string, dst string) error {
	return nil
}

func copytime(src string, dst string) error {
	fi, err := os.Stat(src)
	if err != nil {
		return err
	}
	atime := time.Now() // FIXME:
	mtime := fi.ModTime()
	err = os.Chtimes(dst, atime, mtime)
	if err != nil {
		return err
	}
	return nil
}

func main() {
	flag.Usage = usage
	flag.Parse()
	if flag.NArg() != 2 {
		flag.Usage()
		os.Exit(2)
	}
	srcroot := flag.Arg(0)
	dstroot := flag.Arg(1)
	todo := []func() error{}
	err := filepath.Walk(srcroot, func(src string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		rel, err := filepath.Rel(srcroot, src)
		if err != nil {
			return err
		}
		dst := filepath.Join(dstroot, rel)
		if info.IsDir() {
			err = os.Mkdir(dst, info.Mode())
			if err != nil {
				return err
			}
			err = copyinfo(src, dst)
			if err != nil {
				return err
			}
			// copy time later
			todo = append(todo, func() error {
				return copytime(src, dst)
			})
		} else {
			err = os.Link(src, dst)
			if err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		log.Fatal(err)
	}
	for _, f := range todo {
		err = f()
		if err != nil {
			log.Fatal(err)
		}
	}
}