gitsync.go

package main

import (
	"bufio"
	"flag"
	"log"
	"os/exec"
	"sort"
	"strings"
)

func main() {
	flag.Parse()
	if flag.NArg() != 1 {
		log.Fatal("Usage: gitsync <dest>")
	}
	dest := flag.Arg(0)
	log.Print(dest)
	local, err := getLocalRefs()
	if err != nil {
		log.Fatalf("getting local refs: %v", err)
	}
	remote, err := getRemoteRefs(dest)
	if err != nil {
		log.Fatalf("getting local refs: %v", err)
	}

	var pushRefs []string
	for ref, hash := range local {
		if remote[ref] != hash {
			pushRefs = append(pushRefs, ref)
		}
	}
	sort.Sort(refByPriority(pushRefs))
	for len(pushRefs) > 0 {
		log.Printf("%d refs remain.", len(pushRefs))
		args := []string{"push", "-f", dest}
		n := 0
		for _, ref := range pushRefs {
			args = append(args, "+"+local[ref]+":"+ref)
			n++
			if n == 200 {
				break
			}
		}
		pushRefs = pushRefs[n:]

		log.Printf("git %v", args)
		err := exec.Command("git", args...).Run()
		if err != nil {
			log.Fatal(err)
		}
	}
}

func getLocalRefs() (map[string]string, error) {
	return parseRefs(exec.Command("git", "show-ref"))
}

func getRemoteRefs(dest string) (map[string]string, error) {
	return parseRefs(exec.Command("git", "ls-remote", dest))
}

func parseRefs(cmd *exec.Cmd) (map[string]string, error) {
	refHash := map[string]string{}
	out, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}
	bs := bufio.NewScanner(out)
	if err := cmd.Start(); err != nil {
		return nil, err
	}
	for bs.Scan() {
		f := strings.Fields(bs.Text())
		refHash[f[1]] = f[0]
	}
	return refHash, bs.Err()
}

type refByPriority []string

func (s refByPriority) Len() int      { return len(s) }
func (s refByPriority) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
func (s refByPriority) Less(i, j int) bool {
	p1 := priority[refType(s[i])]
	p2 := priority[refType(s[j])]
	if p1 != p2 {
		return p1 > p2
	}
	return s[i] <= s[j]
}

func refType(s string) string {
	s = strings.TrimPrefix(s, "refs/")
	if i := strings.IndexByte(s, '/'); i != -1 {
		return s[:i]
	}
	return s
}

var priority = map[string]int{
	"heads":   5,
	"tags":    4,
	"changes": 3,
}