### Apps

The core workloads API, which is composed of the DaemonSet, Deployment, ReplicaSet, and StatefulSet kinds, has been promoted to GA stability in the apps/v1 group version. As such, the apps/v1beta2 group version is deprecated, and all new code should use the kinds in the apps/v1 group version.

### Auth

* Kubectl explain now prints out the Kind and API version of the resource being explained. ([#55689](https://github.com/kubernetes/kubernetes/pull/55689), [@luksa](https://github.com/luksa))

### Cluster Lifecycle

* The default Kubernetes version for kubeadm is now 1.10. ([#61127](https://github.com/kubernetes/kubernetes/pull/61127), [@timothysc](https://github.com/timothysc))

- Kubectl version changed to write a warning message to stderr if the client and server version difference exceeds the supported version skew of +/-1 minor version. ([#98250](https://github.com/kubernetes/kubernetes/pull/98250), [@brianpursley](https://github.com/brianpursley)) [SIG CLI]

- The go version defined in `.go-version` is now fetched when invoking test, build, and code generation targets if the current go version does not match it. Set $FORCE_HOST_GO=y while testing or building to skip this behavior, or set $GO_VERSION to override the selected go version. ([#115377](https://github.com/kubernetes/kubernetes/pull/115377), [@liggitt](https://github.com/liggitt)) [SIG Testing]...

### Autoscaling

 - Consuming metrics directly from Heapster is deprecated in favor of
   consuming metrics via an aggregated version of the resource metrics API.

   - In version 1.8, enable this behavior by setting the
     `--horizontal-pod-autoscaler-use-rest-clients` flag to `true`.

- Kubeadm: upgrade supports fallback to the nearest known etcd version if an unknown k8s version is passed ([#88373](https://github.com/kubernetes/kubernetes/pull/88373), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

 
## Changes by Kind

### Deprecation

- Changed `kubectl version` default output to be identical to what `kubectl version --short` printed,
  and removed `--short` flag entirely. ([#116720](https://github.com/kubernetes/kubernetes/pull/116720), [@soltysh](https://github.com/soltysh))

- CRD supports multi-version Schema, Subresources and AdditionalPrintColumns (NOTE that CRDs created prior to 1.13 populated the top-level additionalPrinterColumns field by default. To apply an updated that changes to per-version additionalPrinterColumns, the top-level additionalPrinterColumns field must be explicitly set to null). ([#70211](https://github.com/kubernetes/k...

For stable features, the `kubectl` tool follows the Kubernetes [version skew policy](https://kubernetes.io/releases/version-skew-policy/);
however, kubectl v1.21 and older do not support the new API for ephemeral containers.

- `kubectl api-resources` now prints the API version (as 'API group/version', same as output of `kubectl api-versions`). The column APIGROUP is now APIVERSION ([#95253](https://github.com/kubernetes/kubernetes/pull/95253), [@sallyom](https://github.com/sallyom)) [SIG CLI]