[Docker] Add bash-completion to Dockerfile

[taoyama]

Description

Add bash-completion package for auto completion such as kubectl.

Testing Guide

$ docker build .

History Notes

---

This checklist is used to make sure that common guidelines for a pull request are followed.

• The PR title and description has followed the guideline in Submitting Pull Requests.

• I adhere to the Command Guidelines.

[yungezz]

Thanks for the contribution!

[fengzhou-msft]

@taoyama I built the image and run az acs kubernetes install-cli to install kubectl, then try the autocompletion for kubectl subcommands, but it does not work. Are there any extra settings needed?

[taoyama]

@fengzhou-msft , we need to source completion scripts like this.

$ docker run -it --rm mcr.microsoft.com/azure-cli /bin/bash
bash-5.0# apk add --no-cache bash-completion
fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/community/x86_64/APKINDEX.tar.gz
(1/2) Installing bash-completion (2.9-r0)
(2/2) Installing git-bash-completion (2.24.3-r0)
OK: 220 MiB in 77 packages
bash-5.0# source /etc/profile.d/bash_completion.sh
bash-5.0# az aks install-cli
Downloading client to "/usr/local/bin/kubectl" from "https://storage.googleapis.com/kubernetes-release/release/v1.19.2/bin/linux/amd64/kubectl"
Please ensure that /usr/local/bin is in your search PATH, so the `kubectl` command can be found.
Downloading client to "/tmp/tmpxjg9il_o/kubelogin.zip" from "https://github.com/Azure/kubelogin/releases/download/v0.0.6/kubelogin.zip"
Please ensure that /usr/local/bin is in your search PATH, so the `kubelogin` command can be found.
bash-5.0# source <(kubectl completion bash)
bash-5.0# kubectl
alpha          attach         completion     create         edit           kustomize      plugin         run            uncordon
annotate       auth           config         delete         exec           label          port-forward   scale          version
api-resources  autoscale      convert        describe       explain        logs           proxy          set            wait
api-versions   certificate    cordon         diff           expose         options        replace        taint
apply          cluster-info   cp             drain          get            patch          rollout        top