kubectl config get-contexts をすっきりさせる

おもむろに `kubectl config get-contexts` を打つと

```
CURRENT   NAME                                                        CLUSTER                                                     AUTHINFO                                                   NAMESPACE
          gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app    gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app    gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app    sugi
          gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app   gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app   gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app   sugi2
          gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app   gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app   gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app   sugi3
*         gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app   gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app   gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app
          gke_fugafuga-project2018_asia-east1-a_hands-on                 gke_fugafuga-project2018_asia-east1-a_hands-on                 gke_fugafuga-project2018_asia-east1-a_hands-on
```

こんなことになって、長すぎて見づらいことがあります。これらのクラスタの名前とかは

 ` ~/.kube/config` に定義されていますのでこれを開きます。

こんなの（秘密にした方がよさげなところはマスクしてます）。WindowsでやってるのでWindowsのパスとかも入ってます。

```yaml
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: ひみつ
    server: https://xx.xxx.xxx.xxx
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app
- cluster:
    certificate-authority-data: ひみつ
    server: https://xx.xxx.xxx.xx
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app
- cluster:
    certificate-authority-data: ひみつ
    server: https://xx.xxx.xxx.xxx
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app
- cluster:
    certificate-authority-data: ひみつ
    server: https://xx.xx.xxx.xx
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app
- cluster:
    certificate-authority-data: ひみつ
    server: https://xx.xxx.xxx.xxx
  name: gke_fugafuga-project2018_asia-east1-a_hands-on
contexts:
- context:
    cluster: gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app
    namespace: sugi
    user: gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app
- context:
    cluster: gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app
    namespace: sugi2
    user: gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app
- context:
    cluster: gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app
    namespace: sugi3
    user: gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app
- context:
    cluster: gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app
    user: gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app
  name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app
- context:
    cluster: gke_fugafuga-project2018_asia-east1-a_hands-on
    user: gke_fugafuga-project2018_asia-east1-a_hands-on
  name: gke_fugafuga-project2018_asia-east1-a_hands-on
current-context: gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app
kind: Config
preferences: {}
users:
- name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi-app
  user:
    auth-provider:
      config:
        access-token: ひみつ
        cmd-args: config config-helper --format=json
        cmd-path: C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin\gcloud.cmd
        expiry: 2019-03-18 07:31:28
        expiry-key: '{.credential.token_expiry}'
        token-key: '{.credential.access_token}'
      name: gcp
- name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi2-app
  user:
    auth-provider:
      config:
        access-token: ひみつ
        cmd-args: config config-helper --format=json
        cmd-path: C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin\gcloud.cmd
        expiry: 2019-03-18 09:48:26
        expiry-key: '{.credential.token_expiry}'
        token-key: '{.credential.access_token}'
      name: gcp
- name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi3-app
  user:
    auth-provider:
      config:
        access-token: ひみつ
        cmd-args: config config-helper --format=json
        cmd-path: C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin\gcloud.cmd
        expiry: 2019-04-03 01:30:32
        expiry-key: '{.credential.token_expiry}'
        token-key: '{.credential.access_token}'
      name: gcp
- name: gke_hogehoge-project2019_asia-east1-a_cluster-sugi4-app
  user:
    auth-provider:
      config:
        access-token: ひみつ
        cmd-args: config config-helper --format=json
        cmd-path: C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin\gcloud.cmd
        expiry: 2019-04-03T02:32:11Z
        expiry-key: '{.credential.token_expiry}'
        token-key: '{.credential.access_token}'
      name: gcp
- name: gke_fugafuga-project2018_asia-east1-a_hands-on
  user:
    auth-provider:
      config:
        access-token: ひみつ
        cmd-args: config config-helper --format=json
        cmd-path: C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin\gcloud.cmd
        expiry: 2019-03-15 10:02:27
        expiry-key: '{.credential.token_expiry}'
        token-key: '{.credential.access_token}'
      name: gcp
```
これをみると、クラスタにローカル名を付けて、それをコンテキストで参照してコンテキストにもローカル名を付けて、などで結びついてることが分かります。

たとえばこれを gke_hogehoge-project2019_asia-east1-a_ を削除するように一括置換すると

`kubectl config get-contexts` を打つと

```
CURRENT   NAME                                                        CLUSTER                                                     AUTHINFO                                                   NAMESPACE
          cluster-sugi-app    cluster-sugi-app    cluster-sugi-app    sugi
          cluster-sugi2-app   cluster-sugi2-app   cluster-sugi2-app   sugi2
          cluster-sugi3-app   cluster-sugi3-app   cluster-sugi3-app   sugi3
*         cluster-sugi4-app   cluster-sugi4-app   cluster-sugi4-app
          gke_fugafuga-project2018_asia-east1-a_hands-on                 gke_fugafuga-project2018_asia-east1-a_hands-on                 gke_fugafuga-project2018_asia-east1-a_hands-on
```

こんな感じになって見やすくなります。

一括置換のときはまちがってconfigの別の必要な項目を誤置換しないように長めの文言でやるように気をつけましょう。