.travis, build: autodelete old unstable archives (#13867)

This commit adds a build step to travis to auto-delete unstable archives older than
14 days (our regular release schedule) from Azure via ci.go purge.

The commit also pulls in the latest Azure storage code, also switching over from
the old import path (github.com/Azure/azure-sdk-for-go) to the new split one
(github.com/Azure/azure-storage-go).

build/ci.go

@@ -32,6 +32,7 @@ Available commands are:
    aar        [ -local ] [ -sign key-id ] [-deploy repo] [ -upload dest ]                      -- creates an Android archive
    xcode      [ -local ] [ -sign key-id ] [-deploy repo] [ -upload dest ]                      -- creates an iOS XCode framework
    xgo        [ -alltools ] [ options ]                                                        -- cross builds according to options
+   purge      [ -store blobstore ] [ -days threshold ]                                         -- purges old archives from the blobstore
 
 For all commands, -n prevents execution of external programs (dry run mode).
 
@@ -146,6 +147,8 @@ func main() {
 		doXCodeFramework(os.Args[2:])
 	case "xgo":
 		doXgo(os.Args[2:])
+	case "purge":
+		doPurge(os.Args[2:])
 	default:
 		log.Fatal("unknown command ", os.Args[1])
 	}
@@ -427,6 +430,10 @@ func maybeSkipArchive(env build.Environment) {
 		log.Printf("skipping because this is a PR build")
 		os.Exit(0)
 	}
+	if env.IsCronJob {
+		log.Printf("skipping because this is a cron job")
+		os.Exit(0)
+	}
 	if env.Branch != "master" && !strings.HasPrefix(env.Tag, "v1.") {
 		log.Printf("skipping because branch %q, tag %q is not on the whitelist", env.Branch, env.Tag)
 		os.Exit(0)
@@ -952,3 +959,62 @@ func xgoTool(args []string) *exec.Cmd {
 	}
 	return cmd
 }
+
+// Binary distribution cleanups
+
+func doPurge(cmdline []string) {
+	var (
+		store = flag.String("store", "", `Destination from where to purge archives (usually "gethstore/builds")`)
+		limit = flag.Int("days", 30, `Age threshold above which to delete unstalbe archives`)
+	)
+	flag.CommandLine.Parse(cmdline)
+
+	if env := build.Env(); !env.IsCronJob {
+		log.Printf("skipping because not a cron job")
+		os.Exit(0)
+	}
+	// Create the azure authentication and list the current archives
+	auth := build.AzureBlobstoreConfig{
+		Account:   strings.Split(*store, "/")[0],
+		Token:     os.Getenv("AZURE_BLOBSTORE_TOKEN"),
+		Container: strings.SplitN(*store, "/", 2)[1],
+	}
+	blobs, err := build.AzureBlobstoreList(auth)
+	if err != nil {
+		log.Fatal(err)
+	}
+	// Iterate over the blobs, collect and sort all unstable builds
+	for i := 0; i < len(blobs); i++ {
+		if !strings.Contains(blobs[i].Name, "unstable") {
+			blobs = append(blobs[:i], blobs[i+1:]...)
+			i--
+		}
+	}
+	for i := 0; i < len(blobs); i++ {
+		for j := i + 1; j < len(blobs); j++ {
+			iTime, err := time.Parse(time.RFC1123, blobs[i].Properties.LastModified)
+			if err != nil {
+				log.Fatal(err)
+			}
+			jTime, err := time.Parse(time.RFC1123, blobs[j].Properties.LastModified)
+			if err != nil {
+				log.Fatal(err)
+			}
+			if iTime.After(jTime) {
+				blobs[i], blobs[j] = blobs[j], blobs[i]
+			}
+		}
+	}
+	// Filter out all archives more recent that the given threshold
+	for i, blob := range blobs {
+		timestamp, _ := time.Parse(time.RFC1123, blob.Properties.LastModified)
+		if time.Since(timestamp) < time.Duration(*limit)*24*time.Hour {
+			blobs = blobs[:i]
+			break
+		}
+	}
+	// Delete all marked as such and return
+	if err := build.AzureBlobstoreDelete(auth, blobs); err != nil {
+		log.Fatal(err)
+	}
+}