feat(helm): add --skip-refresh flag to 'helm dep up'

This makes it possible to do a `dep up` without refetching all of
the repositories.While it's less safe, it's useful when doing many
updates in a short period of time (such as in a CI/CD setting)

Closes #2019

cmd/helm/dependency_update.go

@@ -41,11 +41,12 @@ in the requirements.yaml file, but (b) at the wrong version.
 
 // dependencyUpdateCmd describes a 'helm dependency update'
 type dependencyUpdateCmd struct {
-	out       io.Writer
-	chartpath string
-	helmhome  helmpath.Home
-	verify    bool
-	keyring   string
+	out         io.Writer
+	chartpath   string
+	helmhome    helmpath.Home
+	verify      bool
+	keyring     string
+	skipRefresh bool
 }
 
 // newDependencyUpdateCmd creates a new dependency update command.
@@ -80,6 +81,7 @@ func newDependencyUpdateCmd(out io.Writer) *cobra.Command {
 	f := cmd.Flags()
 	f.BoolVar(&duc.verify, "verify", false, "verify the packages against signatures")
 	f.StringVar(&duc.keyring, "keyring", defaultKeyring(), "keyring containing public keys")
+	f.BoolVar(&duc.skipRefresh, "skip-refresh", false, "do not refresh the local repository cache")
 
 	return cmd
 }
@@ -87,10 +89,11 @@ func newDependencyUpdateCmd(out io.Writer) *cobra.Command {
 // run runs the full dependency update process.
 func (d *dependencyUpdateCmd) run() error {
 	man := &downloader.Manager{
-		Out:       d.out,
-		ChartPath: d.chartpath,
-		HelmHome:  d.helmhome,
-		Keyring:   d.keyring,
+		Out:        d.out,
+		ChartPath:  d.chartpath,
+		HelmHome:   d.helmhome,
+		Keyring:    d.keyring,
+		SkipUpdate: d.skipRefresh,
 	}
 	if d.verify {
 		man.Verify = downloader.VerifyIfPossible

cmd/helm/dependency_update_test.go

@@ -128,6 +128,50 @@ func TestDependencyUpdateCmd(t *testing.T) {
 	}
 }
 
+func TestDependencyUpdateCmd_SkipRefresh(t *testing.T) {
+	// Set up a testing helm home
+	oldhome := helmHome
+	hh, err := tempHelmHome(t)
+	if err != nil {
+		t.Fatal(err)
+	}
+	helmHome = hh
+	defer func() {
+		os.RemoveAll(hh)
+		helmHome = oldhome
+	}()
+
+	srv := repotest.NewServer(hh)
+	defer srv.Stop()
+	copied, err := srv.CopyCharts("testdata/testcharts/*.tgz")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("Copied charts:\n%s", strings.Join(copied, "\n"))
+	t.Logf("Listening on directory %s", srv.Root())
+
+	chartname := "depup"
+	if err := createTestingChart(hh, chartname, srv.URL()); err != nil {
+		t.Fatal(err)
+	}
+
+	out := bytes.NewBuffer(nil)
+	duc := &dependencyUpdateCmd{out: out}
+	duc.helmhome = helmpath.Home(hh)
+	duc.chartpath = filepath.Join(hh, chartname)
+	duc.skipRefresh = true
+
+	if err := duc.run(); err == nil {
+		t.Fatal("Expected failure to find the repo with skipRefresh")
+	}
+
+	output := out.String()
+	// This is written directly to stdout, so we have to capture as is.
+	if strings.Contains(output, `update from the "test" chart repository`) {
+		t.Errorf("Repo was unexpectedly updated\n%s", output)
+	}
+}
+
 // createTestingChart creates a basic chart that depends on reqtest-0.1.0
 //
 // The baseURL can be used to point to a particular repository server.

pkg/downloader/manager.go

@@ -53,11 +53,15 @@ type Manager struct {
 	Verify VerificationStrategy
 	// Keyring is the key ring file.
 	Keyring string
+	// SkipUpdate indicates that the repository should not be updated first.
+	SkipUpdate bool
 }
 
 // Build rebuilds a local charts directory from a lockfile.
 //
 // If the lockfile is not present, this will run a Manager.Update()
+//
+// If SkipUpdate is set, this will not update the repository.
 func (m *Manager) Build() error {
 	c, err := m.loadChartDir()
 	if err != nil {
@@ -85,9 +89,11 @@ func (m *Manager) Build() error {
 		return err
 	}
 
-	// For each repo in the file, update the cached copy of that repo
-	if err := m.UpdateRepositories(); err != nil {
-		return err
+	if !m.SkipUpdate {
+		// For each repo in the file, update the cached copy of that repo
+		if err := m.UpdateRepositories(); err != nil {
+			return err
+		}
 	}
 
 	// Now we need to fetch every package here into charts/
@@ -102,7 +108,7 @@ func (m *Manager) Build() error {
 //
 // It first reads the requirements.yaml file, and then attempts to
 // negotiate versions based on that. It will download the versions
-// from remote chart repositories.
+// from remote chart repositories unless SkipUpdate is true.
 func (m *Manager) Update() error {
 	c, err := m.loadChartDir()
 	if err != nil {
@@ -127,8 +133,10 @@ func (m *Manager) Update() error {
 	}
 
 	// For each repo in the file, update the cached copy of that repo
-	if err := m.UpdateRepositories(); err != nil {
-		return err
+	if !m.SkipUpdate {
+		if err := m.UpdateRepositories(); err != nil {
+			return err
+		}
 	}
 
 	// Now we need to find out which version of a chart best satisfies the