Skip upgrades for plugins installed via manifest (#626)

* Skip upgrades for plugins installed via manifest

* Use warning instead of info

Author: chriskim06

cmd/krew/cmd/upgrade.go

@@ -78,6 +78,11 @@ kubectl krew upgrade foo bar"`,
 			var nErrors int
 			for _, name := range pluginNames {
 				indexName, pluginName := pathutil.CanonicalPluginName(name)
+				if indexName == "detached" {
+					klog.Warningf("Skipping upgrade for %q because it was installed via manifest\n", pluginName)
+					continue
+				}
+
 				plugin, err := indexscanner.LoadPluginByName(paths.IndexPluginsPath(indexName), pluginName)
 				if err != nil {
 					if !os.IsNotExist(err) {

integration_test/upgrade_test.go

@@ -81,6 +81,22 @@ func TestKrewUpgradePluginsFromCustomIndex(t *testing.T) {
 	}
 }
 
+func TestKrewUpgradeSkipsManifestPlugin(t *testing.T) {
+	skipShort(t)
+
+	test, cleanup := NewTest(t)
+	defer cleanup()
+
+	test.WithDefaultIndex().
+		Krew("install", "--manifest", filepath.Join("testdata", validPlugin+constants.ManifestExtension)).
+		RunOrFail()
+
+	out := string(test.Krew("upgrade").RunOrFailOutput())
+	if !strings.Contains(out, "Skipping upgrade") {
+		t.Errorf("expected plugin %q to be skipped during upgrade", validPlugin)
+	}
+}
+
 func TestKrewUpgradeNoSecurityWarningForCustomIndex(t *testing.T) {
 	skipShort(t)