travisup.go

package main

import (
	"flag"
	"go/build"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strings"

	yaml "gopkg.in/yaml.v2"
)

const travis = ".travis.yml"

var (
	repo    = flag.String("repo", "", "repository to clone")
	num     = flag.Int("num", 3, "number of most recent versions")
	dry     = flag.Bool("dry", false, "dry run")
	verbose = flag.Bool("v", false, "verbose")
)

func cmd(name string, arg ...string) {
	c := exec.Command(name, arg...)
	if *verbose {
		c.Stdout = os.Stdout
		c.Stderr = os.Stderr
	}
	if err := c.Run(); err != nil {
		log.Fatal(err)
	}
}

func versions(n int) []string {
	v := []string{"1.x"}
	tags := build.Default.ReleaseTags
	for _, tag := range tags[len(tags)-n:] {
		if !strings.HasPrefix(tag, "go1.") {
			log.Fatalf("unexpected relase tag format '%s'", tag)
		}
		v = append(v, tag[2:]+".x")
	}
	return v
}

func main() {
	flag.Parse()

	// Process flags.
	if *repo == "" {
		log.Fatal("must provide repository to clone")
	}

	v := versions(*num)
	log.Print("updating to versions list ", v)

	// Temporary directory.
	dir, err := ioutil.TempDir("", "travisup")
	if err != nil {
		log.Fatal(err)
	}
	defer os.RemoveAll(dir)

	// Clone.
	log.Printf("clone %s", *repo)
	cmd("git", "clone", *repo, dir)

	// Replace versions.
	travispath := filepath.Join(dir, travis)
	b, err := ioutil.ReadFile(travispath)
	if err != nil {
		log.Fatal(err)
	}

	cfg := yaml.MapSlice{}
	if err := yaml.Unmarshal(b, &cfg); err != nil {
		log.Fatal(err)
	}

	for i := range cfg {
		if cfg[i].Key.(string) == "go" {
			cfg[i].Value = v
		}
	}

	b, err = yaml.Marshal(cfg)
	if err != nil {
		log.Fatal(err)
	}

	err = ioutil.WriteFile(travispath, b, 0)
	if err != nil {
		log.Fatal(err)
	}

	if *verbose {
		cmd("git", "-C", dir, "diff")
	}

	// Commit.
	cmd("git", "-C", dir, "add", travis)
	cmd("git", "-C", dir, "commit", "-m", "update go versions in travis")

	// Push.
	if *dry {
		log.Print("dry run skipping push")
		return
	}

	cmd("git", "-C", dir, "push")
}