Add version check

Signed-off-by: Emile Vauge <emile@vauge.com>

version/version.go

@@ -1,5 +1,12 @@
 package version
 
+import (
+	"github.com/containous/traefik/log"
+	"github.com/google/go-github/github"
+	goversion "github.com/hashicorp/go-version"
+	"net/url"
+)
+
 var (
 	// Version holds the current version of traefik.
 	Version = "dev"
@@ -8,3 +15,50 @@ var (
 	// BuildDate holds the build date of traefik.
 	BuildDate = "I don't remember exactly"
 )
+
+// CheckNewVersion checks if a new version is available
+func CheckNewVersion() {
+	if Version == "dev" {
+		return
+	}
+	client := github.NewClient(nil)
+	updateURL, err := url.Parse("https://update.traefik.io")
+	if err != nil {
+		log.Warnf("Error checking new version: %s", err)
+		return
+	}
+	client.BaseURL = updateURL
+	releases, resp, err := client.Repositories.ListReleases("containous", "traefik", nil)
+	if err != nil {
+		log.Warnf("Error checking new version: %s", err)
+		return
+	}
+
+	if resp.StatusCode != 200 {
+		log.Warnf("Error checking new version: status=%s", resp.Status)
+		return
+	}
+
+	currentVersion, err := goversion.NewVersion(Version)
+	if err != nil {
+		log.Warnf("Error checking new version: %s", err)
+		return
+	}
+
+	for _, release := range releases {
+		releaseVersion, err := goversion.NewVersion(*release.TagName)
+		if err != nil {
+			log.Warnf("Error checking new version: %s", err)
+			return
+		}
+
+		if len(currentVersion.Prerelease()) == 0 && len(releaseVersion.Prerelease()) > 0 {
+			continue
+		}
+
+		if releaseVersion.GreaterThan(currentVersion) {
+			log.Warnf("A new release has been found: %s. Please consider updating.", releaseVersion.String())
+			return
+		}
+	}
+}