kubeadm-upgrade: add generated page and include about 'diff'

'kubeadm upgrade diff' is a new sub-command for 1.11:
- Add a generated page for the command line arguments for 'diff'
- Include the generated page in kubeadm-upgrade.md

content/en/docs/reference/setup-tools/kubeadm/generated/kubeadm_upgrade_diff.md

@@ -0,0 +1,38 @@
+
+Show what differences would be applied to existing static pod manifests. See also: kubeadm upgrade apply --dry-run
+
+### Synopsis
+
+Show what differences would be applied to existing static pod manifests. See also: kubeadm upgrade apply --dry-run
+
+```
+kubeadm upgrade diff [version] [flags]
+```
+
+### Options
+
+```
+      --api-server-manifest string           path to API server manifest (default "/etc/kubernetes/manifests/kube-apiserver.yaml")
+  -c, --context-lines int                    How many lines of context in the diff (default 3)
+      --controller-manager-manifest string   path to controller manifest (default "/etc/kubernetes/manifests/kube-controller-manager.yaml")
+  -h, --help                                 help for diff
+      --scheduler-manifest string            path to scheduler manifest (default "/etc/kubernetes/manifests/kube-scheduler.yaml")
+```
+
+### Options inherited from parent commands
+
+```
+      --allow-experimental-upgrades        Show unstable versions of Kubernetes as an upgrade alternative and allow upgrading to an alpha/beta/release candidate versions of Kubernetes.
+      --allow-release-candidate-upgrades   Show release candidate versions of Kubernetes as an upgrade alternative and allow upgrading to a release candidate versions of Kubernetes.
+      --config string                      Path to kubeadm config file. WARNING: Usage of a configuration file is experimental!
+      --feature-gates string               A set of key=value pairs that describe feature gates for various features.Options are:
+                                           Auditing=true|false (ALPHA - default=false)
+                                           CoreDNS=true|false (default=true)
+                                           DynamicKubeletConfig=true|false (ALPHA - default=false)
+                                           SelfHosting=true|false (ALPHA - default=false)
+                                           StoreCertsInSecrets=true|false (ALPHA - default=false)
+      --ignore-preflight-errors strings    A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.
+      --kubeconfig string                  The KubeConfig file to use when talking to the cluster. (default "/etc/kubernetes/admin.conf")
+      --print-config                       Specifies whether the configuration file that will be used in the upgrade should be printed or not.
+```
+

content/en/docs/reference/setup-tools/kubeadm/kubeadm-upgrade.md

@@ -33,6 +33,9 @@ Please check these documents out for more detailed how-to-upgrade guidance:
 ## kubeadm upgrade apply  {#cmd-upgrade-apply}
 {{< include "generated/kubeadm_upgrade_apply.md" >}}
 
+## kubeadm upgrade diff {#cmd-upgrade-diff}
+{{< include "generated/kubeadm_upgrade_diff.md" >}}
+
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