When given a directory, kubectl apply -f <directory> should search a directory recursively for any JSON|YAML files when given a directory. Currently it only finds the immediate children of the given directory.

I believe kubectl apply is exhibiting the same behavior as kubectl create, kubectl delete, etc., but to enable the original #1702 use case of a nested directory of configuration objects being reconciled with the server's state, kubectl apply especially should act recursively.

Current behavior:

$ ls pod/
pod2.yaml  pod.yaml
$ kubectl apply -f pod
pod "nginx-1" configured
pod "nginx-2" configured
$ cd pod
$ mkdir subpod
$ ls
pod2.yaml  pod.yaml  subpod
$ mv * subpod/
$ ls
subpod
$ cd ..
$ kubectl apply -f pod  # everything is now in pod/subpod/*.yaml
error: you must provide one or more resources by argument or filename (.json|.yaml|.yml|stdin)
$

Expected behavior:

$ kubectl apply -f pod  # everything is now in pod/subpod/*.yaml
pod "nginx-1" configured
pod "nginx-2" configured
$