go-ethereum/build/ci.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// +build none

/*
The ci command is called from Continuous Integration scripts.

Usage: go run build/ci.go <command> <command flags/arguments>

Available commands are:

   install    [ -arch architecture ] [ -cc compiler ] [ packages... ]                          -- builds packages and executables
   test       [ -coverage ] [ packages... ]                                                    -- runs the tests
   lint                                                                                        -- runs certain pre-selected linters
   archive    [ -arch architecture ] [ -type zip|tar ] [ -signer key-envvar ] [ -upload dest ] -- archives build artifacts
   importkeys                                                                                  -- imports signing keys from env
   debsrc     [ -signer key-id ] [ -upload dest ]                                              -- creates a debian source package
   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).

*/
package main

import (
	"bytes"
	"encoding/base64"
	"flag"
	"fmt"
	"go/parser"
	"go/token"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"
	"time"

	"github.com/ethersphere/swarm/internal/build"
	sv "github.com/ethersphere/swarm/version"
)

var (
	// Files that end up in the swarm*.zip archive.
	swarmArchiveFiles = []string{
		"COPYING",
		executablePath("swarm"),
	}

	// A debian package is created for all executables listed here.
	debSwarmExecutables = []debExecutable{
		{
			BinaryName:  "swarm",
			PackageName: "ethereum-swarm",
			Description: "Ethereum Swarm daemon and tools",
		},
	}

	debSwarm = debPackage{
		Name:        "ethereum-swarm",
		Version:     sv.Version,
		Executables: debSwarmExecutables,
	}

	// Debian meta packages to build and push to Ubuntu PPA
	debPackages = []debPackage{
		debSwarm,
	}

	// Packages to be cross-compiled by the xgo command
	allCrossCompiledArchiveFiles = swarmArchiveFiles

	// Distros for which packages are created.
	// Note: vivid is unsupported because there is no golang-1.6 package for it.
	// Note: wily is unsupported because it was officially deprecated on lanchpad.
	// Note: yakkety is unsupported because it was officially deprecated on lanchpad.
	// Note: zesty is unsupported because it was officially deprecated on lanchpad.
	// Note: artful is unsupported because it was officially deprecated on lanchpad.
	debDistros = []string{"trusty", "xenial", "bionic", "cosmic"}
)

var GOBIN, _ = filepath.Abs(filepath.Join("build", "bin"))

func executablePath(name string) string {
	if runtime.GOOS == "windows" {
		name += ".exe"
	}
	return filepath.Join(GOBIN, name)
}

func main() {
	log.SetFlags(log.Lshortfile)

	if _, err := os.Stat(filepath.Join("build", "ci.go")); os.IsNotExist(err) {
		log.Fatal("this script must be run from the root of the repository")
	}
	if len(os.Args) < 2 {
		log.Fatal("need subcommand as first argument")
	}
	switch os.Args[1] {
	case "install":
		doInstall(os.Args[2:])
	case "test":
		doTest(os.Args[2:])
	case "lint":
		doLint(os.Args[2:])
	case "archive":
		doArchive(os.Args[2:])
	case "debsrc":
		doDebianSource(os.Args[2:])
	case "xgo":
		doXgo(os.Args[2:])
	case "purge":
		doPurge(os.Args[2:])
	default:
		log.Fatal("unknown command ", os.Args[1])
	}
}

// Compiling

func doInstall(cmdline []string) {
	var (
		arch = flag.String("arch", "", "Architecture to cross build for")
		cc   = flag.String("cc", "", "C compiler to cross build with")
	)
	flag.CommandLine.Parse(cmdline)
	env := build.Env()

	// Check Go version. People regularly open issues about compilation
	// failure with outdated Go. This should save them the trouble.
	if !strings.Contains(runtime.Version(), "devel") {
		// Figure out the minor version number since we can't textually compare (1.10 < 1.9)
		var minor int
		fmt.Sscanf(strings.TrimPrefix(runtime.Version(), "go1."), "%d", &minor)

		if minor < 9 {
			log.Println("You have Go version", runtime.Version())
			log.Println("go-ethereum requires at least Go version 1.9 and cannot")
			log.Println("be compiled with an earlier version. Please upgrade your Go installation.")
			os.Exit(1)
		}
	}
	// Compile packages given as arguments, or everything if there are no arguments.
	packages := []string{"./..."}
	if flag.NArg() > 0 {
		packages = flag.Args()
	}
	packages = build.ExpandPackagesNoVendor(packages)

	if *arch == "" || *arch == runtime.GOARCH {
		goinstall := goTool("install", buildFlags(env)...)
		goinstall.Args = append(goinstall.Args, "-v")
		goinstall.Args = append(goinstall.Args, packages...)
		build.MustRun(goinstall)
		return
	}
	// If we are cross compiling to ARMv5 ARMv6 or ARMv7, clean any previous builds
	if *arch == "arm" {
		os.RemoveAll(filepath.Join(runtime.GOROOT(), "pkg", runtime.GOOS+"_arm"))
		for _, path := range filepath.SplitList(build.GOPATH()) {
			os.RemoveAll(filepath.Join(path, "pkg", runtime.GOOS+"_arm"))
		}
	}
	// Seems we are cross compiling, work around forbidden GOBIN
	goinstall := goToolArch(*arch, *cc, "install", buildFlags(env)...)
	goinstall.Args = append(goinstall.Args, "-v")
	goinstall.Args = append(goinstall.Args, []string{"-buildmode", "archive"}...)
	goinstall.Args = append(goinstall.Args, packages...)
	build.MustRun(goinstall)

	if cmds, err := ioutil.ReadDir("cmd"); err == nil {
		for _, cmd := range cmds {
			pkgs, err := parser.ParseDir(token.NewFileSet(), filepath.Join(".", "cmd", cmd.Name()), nil, parser.PackageClauseOnly)
			if err != nil {
				log.Fatal(err)
			}
			for name := range pkgs {
				if name == "main" {
					gobuild := goToolArch(*arch, *cc, "build", buildFlags(env)...)
					gobuild.Args = append(gobuild.Args, "-v")
					gobuild.Args = append(gobuild.Args, []string{"-o", executablePath(cmd.Name())}...)
					gobuild.Args = append(gobuild.Args, "."+string(filepath.Separator)+filepath.Join("cmd", cmd.Name()))
					build.MustRun(gobuild)
					break
				}
			}
		}
	}
}

func buildFlags(env build.Environment) (flags []string) {
	var ld []string
	if env.Commit != "" {
		ld = append(ld, "-X", "main.gitCommit="+env.Commit)
	}
	if runtime.GOOS == "darwin" {
		ld = append(ld, "-s")
	}

	if len(ld) > 0 {
		flags = append(flags, "-ldflags", strings.Join(ld, " "))
	}
	return flags
}

func goTool(subcmd string, args ...string) *exec.Cmd {
	return goToolArch(runtime.GOARCH, os.Getenv("CC"), subcmd, args...)
}

func goToolArch(arch string, cc string, subcmd string, args ...string) *exec.Cmd {
	cmd := build.GoTool(subcmd, args...)
	cmd.Env = []string{"GOPATH=" + build.GOPATH()}
	if arch == "" || arch == runtime.GOARCH {
		cmd.Env = append(cmd.Env, "GOBIN="+GOBIN)
	} else {
		cmd.Env = append(cmd.Env, "CGO_ENABLED=1")
		cmd.Env = append(cmd.Env, "GOARCH="+arch)
	}
	if cc != "" {
		cmd.Env = append(cmd.Env, "CC="+cc)
	}
	for _, e := range os.Environ() {
		if strings.HasPrefix(e, "GOPATH=") || strings.HasPrefix(e, "GOBIN=") {
			continue
		}
		cmd.Env = append(cmd.Env, e)
	}
	return cmd
}

// Running The Tests
//
// "tests" also includes static analysis tools such as vet.

func doTest(cmdline []string) {
	coverage := flag.Bool("coverage", false, "Whether to record code coverage")
	flag.CommandLine.Parse(cmdline)
	env := build.Env()

	packages := []string{"./..."}
	if len(flag.CommandLine.Args()) > 0 {
		packages = flag.CommandLine.Args()
	}
	packages = build.ExpandPackagesNoVendor(packages)

	// Run the actual tests.
	// Test a single package at a time. CI builders are slow
	// and some tests run into timeouts under load.
	gotest := goTool("test", buildFlags(env)...)
	gotest.Args = append(gotest.Args, "-p", "1", "-timeout", "5m")
	if *coverage {
		gotest.Args = append(gotest.Args, "-covermode=atomic", "-cover")
	}

	gotest.Args = append(gotest.Args, packages...)
	build.MustRun(gotest)
}

// runs gometalinter on requested packages
func doLint(cmdline []string) {
	flag.CommandLine.Parse(cmdline)

	packages := []string{"./..."}
	if len(flag.CommandLine.Args()) > 0 {
		packages = flag.CommandLine.Args()
	}
	// Get metalinter and install all supported linters
	build.MustRun(goTool("get", "gopkg.in/alecthomas/gometalinter.v2"))
	build.MustRunCommand(filepath.Join(GOBIN, "gometalinter.v2"), "--install")

	// Run fast linters batched together
	configs := []string{
		"--vendor",
		"--tests",
		"--deadline=2m",
		"--disable-all",
		"--enable=goimports",
		"--enable=varcheck",
		"--enable=vet",
		"--enable=gofmt",
		"--enable=misspell",
		"--enable=goconst",
		"--min-occurrences=6", // for goconst
	}
	build.MustRunCommand(filepath.Join(GOBIN, "gometalinter.v2"), append(configs, packages...)...)

	// Run slow linters one by one
	for _, linter := range []string{"unconvert", "gosimple"} {
		configs = []string{"--vendor", "--tests", "--deadline=10m", "--disable-all", "--enable=" + linter}
		build.MustRunCommand(filepath.Join(GOBIN, "gometalinter.v2"), append(configs, packages...)...)
	}
}

// Release Packaging
func doArchive(cmdline []string) {
	var (
		arch   = flag.String("arch", runtime.GOARCH, "Architecture cross packaging")
		atype  = flag.String("type", "zip", "Type of archive to write (zip|tar)")
		signer = flag.String("signer", "", `Environment variable holding the signing key (e.g. LINUX_SIGNING_KEY)`)
		upload = flag.String("upload", "", `Destination to upload the archives (usually "ethswarm/builds")`)
		ext    string
	)
	flag.CommandLine.Parse(cmdline)
	switch *atype {
	case "zip":
		ext = ".zip"
	case "tar":
		ext = ".tar.gz"
	default:
		log.Fatal("unknown archive type: ", atype)
	}

	var (
		env = build.Env()

		baseswarm = archiveBasename(*arch, sv.ArchiveVersion(env.Commit))
		swarm     = "swarm-" + baseswarm + ext
	)
	maybeSkipArchive(env)

	if err := build.WriteArchive(swarm, swarmArchiveFiles); err != nil {
		log.Fatal(err)
	}
	for _, archive := range []string{swarm} {
		if err := archiveUpload(archive, *upload, *signer); err != nil {
			log.Fatal(err)
		}
	}
}

func archiveBasename(arch string, archiveVersion string) string {
	platform := runtime.GOOS + "-" + arch
	if arch == "arm" {
		platform += os.Getenv("GOARM")
	}
	return platform + "-" + archiveVersion
}

func archiveUpload(archive string, blobstore string, signer string) error {
	// If signing was requested, generate the signature files
	if signer != "" {
		key := getenvBase64(signer)
		if err := build.PGPSignFile(archive, archive+".asc", string(key)); err != nil {
			return err
		}
	}
	// If uploading to Azure was requested, push the archive possibly with its signature
	if blobstore != "" {
		auth := build.AzureBlobstoreConfig{
			Account:   strings.Split(blobstore, "/")[0],
			Token:     os.Getenv("AZURE_BLOBSTORE_TOKEN"),
			Container: strings.SplitN(blobstore, "/", 2)[1],
		}
		if err := build.AzureBlobstoreUpload(archive, filepath.Base(archive), auth); err != nil {
			return err
		}
		if signer != "" {
			if err := build.AzureBlobstoreUpload(archive+".asc", filepath.Base(archive+".asc"), auth); err != nil {
				return err
			}
		}
	}
	return nil
}

// skips archiving for some build configurations.
func maybeSkipArchive(env build.Environment) {
	if env.IsPullRequest {
		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)
	}
	validArchiveTag, _ := regexp.MatchString("v([0-9]+).([0-9]+).([0-9]+)", "v10.2.3")

	if env.Branch != "master" && !validArchiveTag {
		log.Printf("skipping because branch %q, tag %q is not on the whitelist", env.Branch, env.Tag)
		os.Exit(0)
	}
}

// Debian Packaging
func doDebianSource(cmdline []string) {
	var (
		signer  = flag.String("signer", "", `Signing key name, also used as package author`)
		upload  = flag.String("upload", "", `Where to upload the source package (usually "ethereum/ethereum")`)
		sshUser = flag.String("sftp-user", "", `Username for SFTP upload (usually "geth-ci")`)
		workdir = flag.String("workdir", "", `Output directory for packages (uses temp dir if unset)`)
		now     = time.Now()
	)
	flag.CommandLine.Parse(cmdline)
	*workdir = makeWorkdir(*workdir)
	env := build.Env()
	maybeSkipArchive(env)

	// Import the signing key.
	if key := getenvBase64("PPA_SIGNING_KEY"); len(key) > 0 {
		gpg := exec.Command("gpg", "--import")
		gpg.Stdin = bytes.NewReader(key)
		build.MustRun(gpg)
	}

	// Create Debian packages and upload them
	for _, pkg := range debPackages {
		for _, distro := range debDistros {
			meta := newDebMetadata(distro, *signer, env, now, pkg.Name, pkg.Version, pkg.Executables)
			pkgdir := stageDebianSource(*workdir, meta)
			debuild := exec.Command("debuild", "-S", "-sa", "-us", "-uc", "-d", "-Zxz")
			debuild.Dir = pkgdir
			build.MustRun(debuild)

			var (
				basename  = fmt.Sprintf("%s_%s", meta.Name(), meta.VersionString())
				source    = filepath.Join(*workdir, basename+".tar.xz")
				dsc       = filepath.Join(*workdir, basename+".dsc")
				changes   = filepath.Join(*workdir, basename+"_source.changes")
				buildinfo = filepath.Join(*workdir, basename+"_source.buildinfo")
			)
			if *signer != "" {
				build.MustRunCommand("debsign", changes)
			}
			if *upload != "" {
				ppaUpload(*workdir, *upload, *sshUser, []string{source, dsc, changes, buildinfo})
			}
		}
	}
}

func ppaUpload(workdir, ppa, sshUser string, files []string) {
	p := strings.Split(ppa, "/")
	if len(p) != 2 {
		log.Fatal("-upload PPA name must contain single /")
	}
	if sshUser == "" {
		sshUser = p[0]
	}
	incomingDir := fmt.Sprintf("~%s/ubuntu/%s", p[0], p[1])
	// Create the SSH identity file if it doesn't exist.
	var idfile string
	if sshkey := getenvBase64("PPA_SSH_KEY"); len(sshkey) > 0 {
		idfile = filepath.Join(workdir, "sshkey")
		if _, err := os.Stat(idfile); os.IsNotExist(err) {
			ioutil.WriteFile(idfile, sshkey, 0600)
		}
	}
	// Upload
	dest := sshUser + "@ppa.launchpad.net"
	if err := build.UploadSFTP(idfile, dest, incomingDir, files); err != nil {
		log.Fatal(err)
	}
}

func getenvBase64(variable string) []byte {
	dec, err := base64.StdEncoding.DecodeString(os.Getenv(variable))
	if err != nil {
		log.Fatal("invalid base64 " + variable)
	}
	return []byte(dec)
}

func makeWorkdir(wdflag string) string {
	var err error
	if wdflag != "" {
		err = os.MkdirAll(wdflag, 0744)
	} else {
		wdflag, err = ioutil.TempDir("", "geth-build-")
	}
	if err != nil {
		log.Fatal(err)
	}
	return wdflag
}

func isUnstableBuild(env build.Environment) bool {
	if env.Tag != "" {
		return false
	}
	return true
}

type debPackage struct {
	Name        string          // the name of the Debian package to produce, e.g. "ethereum", or "ethereum-swarm"
	Version     string          // the clean version of the debPackage, e.g. 1.8.12 or 0.3.0, without any metadata
	Executables []debExecutable // executables to be included in the package
}

type debMetadata struct {
	Env build.Environment

	PackageName string

	// go-ethereum version being built. Note that this
	// is not the debian package version. The package version
	// is constructed by VersionString.
	Version string

	Author       string // "name <email>", also selects signing key
	Distro, Time string
	Executables  []debExecutable
}

type debExecutable struct {
	PackageName string
	BinaryName  string
	Description string
}

// Package returns the name of the package if present, or
// fallbacks to BinaryName
func (d debExecutable) Package() string {
	if d.PackageName != "" {
		return d.PackageName
	}
	return d.BinaryName
}

func newDebMetadata(distro, author string, env build.Environment, t time.Time, name string, version string, exes []debExecutable) debMetadata {
	if author == "" {
		// No signing key, use default author.
		author = "Ethereum Builds <fjl@ethereum.org>"
	}
	return debMetadata{
		PackageName: name,
		Env:         env,
		Author:      author,
		Distro:      distro,
		Version:     version,
		Time:        t.Format(time.RFC1123Z),
		Executables: exes,
	}
}

// Name returns the name of the metapackage that depends
// on all executable packages.
func (meta debMetadata) Name() string {
	if isUnstableBuild(meta.Env) {
		return meta.PackageName + "-unstable"
	}
	return meta.PackageName
}

// VersionString returns the debian version of the packages.
func (meta debMetadata) VersionString() string {
	vsn := meta.Version
	if meta.Env.Buildnum != "" {
		vsn += "+build" + meta.Env.Buildnum
	}
	if meta.Distro != "" {
		vsn += "+" + meta.Distro
	}
	return vsn
}

// ExeList returns the list of all executable packages.
func (meta debMetadata) ExeList() string {
	names := make([]string, len(meta.Executables))
	for i, e := range meta.Executables {
		names[i] = meta.ExeName(e)
	}
	return strings.Join(names, ", ")
}

// ExeName returns the package name of an executable package.
func (meta debMetadata) ExeName(exe debExecutable) string {
	if isUnstableBuild(meta.Env) {
		return exe.Package() + "-unstable"
	}
	return exe.Package()
}

// ExeConflicts returns the content of the Conflicts field
// for executable packages.
func (meta debMetadata) ExeConflicts(exe debExecutable) string {
	if isUnstableBuild(meta.Env) {
		// Set up the conflicts list so that the *-unstable packages
		// cannot be installed alongside the regular version.
		//
		// https://www.debian.org/doc/debian-policy/ch-relationships.html
		// is very explicit about Conflicts: and says that Breaks: should
		// be preferred and the conflicting files should be handled via
		// alternates. We might do this eventually but using a conflict is
		// easier now.
		return "ethereum, " + exe.Package()
	}
	return ""
}

func stageDebianSource(tmpdir string, meta debMetadata) (pkgdir string) {
	pkg := meta.Name() + "-" + meta.VersionString()
	pkgdir = filepath.Join(tmpdir, pkg)
	if err := os.Mkdir(pkgdir, 0755); err != nil {
		log.Fatal(err)
	}

	// Copy the source code.
	build.MustRunCommand("git", "checkout-index", "-a", "--prefix", pkgdir+string(filepath.Separator))

	// Put the debian build files in place.
	debian := filepath.Join(pkgdir, "debian")
	build.Render("build/deb/"+meta.PackageName+"/deb.rules", filepath.Join(debian, "rules"), 0755, meta)
	build.Render("build/deb/"+meta.PackageName+"/deb.changelog", filepath.Join(debian, "changelog"), 0644, meta)
	build.Render("build/deb/"+meta.PackageName+"/deb.control", filepath.Join(debian, "control"), 0644, meta)
	build.Render("build/deb/"+meta.PackageName+"/deb.copyright", filepath.Join(debian, "copyright"), 0644, meta)
	build.RenderString("8\n", filepath.Join(debian, "compat"), 0644, meta)
	build.RenderString("3.0 (native)\n", filepath.Join(debian, "source/format"), 0644, meta)
	for _, exe := range meta.Executables {
		install := filepath.Join(debian, meta.ExeName(exe)+".install")
		docs := filepath.Join(debian, meta.ExeName(exe)+".docs")
		build.Render("build/deb/"+meta.PackageName+"/deb.install", install, 0644, exe)
		build.Render("build/deb/"+meta.PackageName+"/deb.docs", docs, 0644, exe)
	}

	return pkgdir
}

// Cross compilation

func doXgo(cmdline []string) {
	var (
		alltools = flag.Bool("alltools", false, `Flag whether we're building all known tools, or only on in particular`)
	)
	flag.CommandLine.Parse(cmdline)
	env := build.Env()

	// Make sure xgo is available for cross compilation
	gogetxgo := goTool("get", "github.com/karalabe/xgo")
	build.MustRun(gogetxgo)

	// If all tools building is requested, build everything the builder wants
	args := append(buildFlags(env), flag.Args()...)

	if *alltools {
		args = append(args, []string{"--dest", GOBIN}...)
		for _, res := range allCrossCompiledArchiveFiles {
			if strings.HasPrefix(res, GOBIN) {
				// Binary tool found, cross build it explicitly
				args = append(args, "./"+filepath.Join("cmd", filepath.Base(res)))
				xgo := xgoTool(args)
				build.MustRun(xgo)
				args = args[:len(args)-1]
			}
		}
		return
	}
	// Otherwise xxecute the explicit cross compilation
	path := args[len(args)-1]
	args = append(args[:len(args)-1], []string{"--dest", GOBIN, path}...)

	xgo := xgoTool(args)
	build.MustRun(xgo)
}

func xgoTool(args []string) *exec.Cmd {
	cmd := exec.Command(filepath.Join(GOBIN, "xgo"), args...)
	cmd.Env = []string{
		"GOPATH=" + build.GOPATH(),
		"GOBIN=" + GOBIN,
	}
	for _, e := range os.Environ() {
		if strings.HasPrefix(e, "GOPATH=") || strings.HasPrefix(e, "GOBIN=") {
			continue
		}
		cmd.Env = append(cmd.Env, e)
	}
	return cmd
}

// Binary distribution cleanups

func doPurge(cmdline []string) {
	var (
		store = flag.String("store", "", `Destination from where to purge archives (usually "ethswarm/builds")`)
		limit = flag.Int("days", 30, `Age threshold above which to delete unstable 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++ {
			if blobs[i].Properties.LastModified.After(blobs[j].Properties.LastModified) {
				blobs[i], blobs[j] = blobs[j], blobs[i]
			}
		}
	}
	// Filter out all archives more recent that the given threshold
	for i, blob := range blobs {
		if time.Since(blob.Properties.LastModified) < 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)
	}
}