Fix version comparison in upgrade

cmd/syncthing/upgrade.go

@@ -0,0 +1,170 @@
+package main
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+
+	"bytes"
+	"bitbucket.org/kardianos/osext"
+)
+
+type githubRelease struct {
+	Tag      string        `json:"tag_name"`
+	Prelease bool          `json:"prerelease"`
+	Assets   []githubAsset `json:"assets"`
+}
+
+type githubAsset struct {
+	URL  string `json:"url"`
+	Name string `json:"name"`
+}
+
+var GoArchExtra string // "", "v5", "v6", "v7"
+
+func upgrade() error {
+	if runtime.GOOS == "windows" {
+		return errors.New("Upgrade currently unsupported on Windows")
+	}
+
+	path, err := osext.Executable()
+	if err != nil {
+		return err
+	}
+
+	resp, err := http.Get("https://api.github.com/repos/calmh/syncthing/releases?per_page=1")
+	if err != nil {
+		return err
+	}
+
+	var rels []githubRelease
+	json.NewDecoder(resp.Body).Decode(&rels)
+	resp.Body.Close()
+
+	if len(rels) != 1 {
+		return fmt.Errorf("Unexpected number of releases: %d", len(rels))
+	}
+	rel := rels[0]
+
+	switch compareVersions(rel.Tag, Version) {
+	case -1:
+		l.Okf("Current version %s is newer than latest release %s. Not upgrading.", Version, rel.Tag)
+		return nil
+	case 0:
+		l.Okf("Already running the latest version, %s. Not upgrading.", Version)
+		return nil
+	default:
+		l.Infof("Attempting upgrade to %s...", rel.Tag)
+	}
+
+	expectedRelease := fmt.Sprintf("syncthing-%s-%s%s-%s.", runtime.GOOS, runtime.GOARCH, GoArchExtra, rel.Tag)
+	for _, asset := range rel.Assets {
+		if strings.HasPrefix(asset.Name, expectedRelease) {
+			if strings.HasSuffix(asset.Name, ".tar.gz") {
+				l.Infof("Downloading %s...", asset.Name)
+				fname, err := readTarGZ(asset.URL, filepath.Dir(path))
+				if err != nil {
+					return err
+				}
+
+				old := path + "." + Version
+				err = os.Rename(path, old)
+				if err != nil {
+					return err
+				}
+				err = os.Rename(fname, path)
+				if err != nil {
+					return err
+				}
+
+				l.Okf("Upgraded %q to %s.", path, rel.Tag)
+				l.Okf("Previous version saved in %q.", old)
+
+				return nil
+			}
+		}
+	}
+
+	l.Warnf("Found no asset for %q", expectedRelease)
+	return nil
+}
+
+func readTarGZ(url string, dir string) (string, error) {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return "", err
+	}
+
+	req.Header.Add("Accept", "application/octet-stream")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	gr, err := gzip.NewReader(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	tr := tar.NewReader(gr)
+	if err != nil {
+		return "", err
+	}
+
+	// Iterate through the files in the archive.
+	for {
+		hdr, err := tr.Next()
+		if err == io.EOF {
+			// end of tar archive
+			break
+		}
+		if err != nil {
+			return "", err
+		}
+
+		if path.Base(hdr.Name) == "syncthing" {
+			of, err := ioutil.TempFile(dir, "syncthing")
+			if err != nil {
+				return "", err
+			}
+			io.Copy(of, tr)
+			err = of.Close()
+			if err != nil {
+				os.Remove(of.Name())
+				return "", err
+			}
+
+			os.Chmod(of.Name(), os.FileMode(hdr.Mode))
+			return of.Name(), nil
+		}
+	}
+
+	return "", fmt.Errorf("No upgrade found")
+}
+
+func compareVersions(a, b string) int {
+	return bytes.Compare(versionParts(a), versionParts(b))
+}
+
+func versionParts(v string) []byte {
+	parts := strings.Split(v, "-")
+	fields := strings.Split(parts[0], ".")
+	res := make([]byte, len(fields))
+	for i, s := range fields {
+		v, _ := strconv.Atoi(s)
+		res[i] = byte(v)
+	}
+	return res
+}