- Client-go: Optimized leaders renewing leases by updating leader lock optimistically without getting the record from the API server first. Also, a new metric `leader_election_slowpath_total` was added to allow users to monitor how many leader elections are updated non-optimistically.

* Add "deploy" abbrev for deployments to kubectl ([#24087](https://github.com/kubernetes/kubernetes/pull/24087), [@Frostman](https://github.com/Frostman))
* --no-header available now for custom-column ([#26696](https://github.com/kubernetes/kubernetes/pull/26696), [@gitfred](https://github.com/gitfred))



# v1.4.0-alpha.1

* Reduce time needed to attach Azure disks ([#40066](https://github.com/kubernetes/kubernetes/pull/40066), [@codablock](https://github.com/codablock))
* Fixes request header authenticator by presenting the request header client CA so that the front proxy will authenticate using its client certificate. ([#40301](https://github.com/kubernetes/kubernetes/pull/40301), [@deads2k](https://github.com/deads2k))