Generate context and user name smartly when merging config

[yujunz]

Is your feature request related to a problem? Please describe.
I'm always frustrated when merging config produces random context names, e.g.

Loading KubeConfig file: /Users/yujunz/.kube/config
Add Context: config-ktd65k9dkh
Add Context: config-9bbc58ghm5
Add Context: config-7864ft646m
Add Context: config-4hd4hd7cd7
Add Context: config-k6hh45mbt5
Add Context: config-mg6mch5976
Add Context: config-6kf6g9mbc4

and duplicated users

name: vault-user
  user:
    client-certificate: client.crt
    client-key: client
- name: vault-user-7864ft646m
  user:
    client-certificate: client.crt
    client-key: client
- name: vault-user-k6hh45mbt5
  user:
    client-certificate: client.crt
    client-key: client

Describe the solution you'd like
Format the context from cluster and user name, e.g. user@cluster or simply cluster when there is no ambiguity.

Describe alternatives you've considered
Allow user to define the format string

Additional context
N/A

[yujunz]

kubecm merge ~/.kube/dev0.config ~/.kube/stg0.config ~/.kube/config
Loading KubeConfig file: /Users/yujunz/.kube/dev0.config
Add Context: dev0
Loading KubeConfig file: /Users/yujunz/.kube/stg0.config
Add Context: stg0
Loading KubeConfig file: /Users/yujunz/.kube/config
Add Context: config-4cc9fbm2f6
Add Context: config-ktd65k9dkh
Add Context: config-7d78g685c4
Add Context: config-d5btdk9gc8
Add Context: config-22h4ktfc5b
Add Context: config-5ftf6hdm4g

Currently it renames the existing context to random strings which is quite annoying.

[sunny0826]

It's a historical problem. Thanks for the feedback, I'll follow up by refactoring this part of the code.

[FeryET]

Is there anyway to keep the name of contexts in case of merging? I have unique context names in various files that I want to keep after merging.

[sunny0826]

Sorry this hasn't been fixed yet due to work changes, I'll try to open this up in the near future.

[sunny0826]

/assign @cr7258

[cr7258]

I'll work on it.