From 5adee740008a65907bfd8d6e3c3275e24f23f27d Mon Sep 17 00:00:00 2001
From: "Lubomir I. Ivanov" <lubomirivanov@vmware.com>
Date: Thu, 17 May 2018 20:39:21 +0300
Subject: [PATCH] kubeadm-upgrade: small improvements to diff

1) Store the io.Writer and pass it to sub-commands in upgrade.go
2) Check if the manifest path is an empty string in diff.go:runDiff()
3) Use the io.Writer that upgrade.go defines instead of writing to
os.Stdout directly.
---
 cmd/kubeadm/app/cmd/upgrade/diff.go    | 7 +++++--
 cmd/kubeadm/app/cmd/upgrade/upgrade.go | 2 ++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/cmd/kubeadm/app/cmd/upgrade/diff.go b/cmd/kubeadm/app/cmd/upgrade/diff.go
index 957b05f72ee..cf87756c678 100644
--- a/cmd/kubeadm/app/cmd/upgrade/diff.go
+++ b/cmd/kubeadm/app/cmd/upgrade/diff.go
@@ -17,8 +17,8 @@ limitations under the License.
 package upgrade
 
 import (
+	"fmt"
 	"io/ioutil"
-	"os"
 
 	"github.com/golang/glog"
 	"github.com/pmezard/go-difflib/difflib"
@@ -119,6 +119,9 @@ func runDiff(flags *diffFlags, args []string) error {
 		if err != nil {
 			return err
 		}
+		if path == "" {
+			return fmt.Errorf("empty manifest path")
+		}
 		existingManifest, err := ioutil.ReadFile(path)
 		if err != nil {
 			return err
@@ -133,7 +136,7 @@ func runDiff(flags *diffFlags, args []string) error {
 			Context:  flags.contextLines,
 		}
 
-		difflib.WriteUnifiedDiff(os.Stdout, diff)
+		difflib.WriteUnifiedDiff(flags.parent.out, diff)
 	}
 	return nil
 }
diff --git a/cmd/kubeadm/app/cmd/upgrade/upgrade.go b/cmd/kubeadm/app/cmd/upgrade/upgrade.go
index 1993e67a22e..a7928aa01bc 100644
--- a/cmd/kubeadm/app/cmd/upgrade/upgrade.go
+++ b/cmd/kubeadm/app/cmd/upgrade/upgrade.go
@@ -37,6 +37,7 @@ type cmdUpgradeFlags struct {
 	skipPreFlight             bool
 	ignorePreflightErrors     []string
 	ignorePreflightErrorsSet  sets.String
+	out                       io.Writer
 }
 
 // NewCmdUpgrade returns the cobra command for `kubeadm upgrade`
@@ -50,6 +51,7 @@ func NewCmdUpgrade(out io.Writer) *cobra.Command {
 		printConfig:               false,
 		skipPreFlight:             false,
 		ignorePreflightErrorsSet:  sets.NewString(),
+		out: out,
 	}
 
 	cmd := &cobra.Command{