- Added `--output plaintext-openapiv2` argument to kubectl explain to use old openapiv2 `explain` implementation. ([#115480](https://github.com/kubernetes/kubernetes/pull/115480), [@alexzielenski](https://github.com/alexzielenski))

### Other (Cleanup or Flake)

- Added a short output format argument for `kubectl explain`. You could now use `-o` as an abbreviation for `--output` in commands such as `kubectl explain <resource> --output plaintext-openapiv2`. ([#127869](https://github.com/kubernetes/kubernetes/pull/127869), [@ak20102763](https://github.com/ak20102763))

* `crds` has been added as a shortname for CustomResourceDefinition, as in `kubectl get crds` ([#59061](https://github.com/kubernetes/kubernetes/pull/59061), [@nikhita](https://github.com/nikhita))

* Fix kubectl explain for resources not existing in default version of API group, such as  `batch/v1, Kind=CronJob`. ([#58753](https://github.com/kubernetes/kubernetes/pull/58753), [@soltysh](https://github.com/soltysh))

- Fixed bug where explain was not properly respecting jsonpaths. ([#115694](https://github.com/kubernetes/kubernetes/pull/115694), [@mpuckett159](https://github.com/mpuckett159))

- The shorthand for --output flag in kubectl explain was accidentally deleted, but has been added back. ([#131962](https://github.com/kubernetes/kubernetes/pull/131962), [@superbrothers](https://github.com/superbrothers)) [SIG CLI]

*   `kubectl explain` now explains `apiservices` and `customresourcedefinition`. (Updated to use OpenAPI instead of Swagger 1.2.) ([#53228](https://github.com/kubernetes/kubernetes/pull/53228),[ @apelisse](https://github.com/apelisse))

- Fixed `kubectl explain` to show enum for field types if they were defined. ([#123023](https://github.com/kubernetes/kubernetes/pull/123023), [@ah8ad3](https://github.com/ah8ad3))

- The shorthand for --output flag in kubectl explain was accidentally deleted, but has been added back. ([#131993](https://github.com/kubernetes/kubernetes/pull/131993), [@superbrothers](https://github.com/superbrothers)) [SIG CLI]

### Other (Cleanup or Flake)

#### CustomResourceDefinition OpenAPI Publishing

OpenAPI specs for native types have long been served at /openapi/v2, and they are consumed by a number of components, notably kubectl client-side validation, kubectl explain and OpenAPI based client generators.

With Kubernetes 1.15 as beta, OpenAPI schemas are also published for CRDs, as long as their schemas are structural.

    <glob pattern="*.xconf"/>
    <sub-class-of type="text/plain"/>
  </mime-type>

  <mime-type type="text/css">
    <_comment>Cascading Style Sheet</_comment>
    <glob pattern="*.css"/>
    <sub-class-of type="text/plain"/>
  </mime-type>

  <mime-type type="text/csv">
    <glob pattern="*.csv"/>
    <sub-class-of type="text/plain"/>
  </mime-type>

  <mime-type type="text/directory"/>