kube-ps1: update to latest upstream version (c685ac8)

Closes #8009
Co-authored-by: Jon Mosco <jonny.mosco@gmail.com>

plugins/kube-ps1/README.md

-# Kubernetes prompt for zsh
+kube-ps1: Kubernetes prompt for bash and zsh
+============================================
 
-A Kubernetes zsh prompt that displays the current cluster cluster
-and the namespace.
+A script that lets you add the current Kubernetes context and namespace
+configured on `kubectl` to your Bash/Zsh prompt strings (i.e. the `$PS1`).
 
-Inspired by several tools used to simplify usage of kubectl
+Inspired by several tools used to simplify usage of `kubectl`.
 
-NOTE: If you are not using zsh, check out [kube-ps1](https://github.com/jonmosco/kube-ps1)
-designed for bash as well as zsh.
+![prompt](img/screenshot2.png)
 
-## Requirements
-
-The default prompt assumes you have the kubectl command line utility installed.  It
-can be obtained here:
+![prompt_sol_light](img/screenshot-sol-light.png)
 
-[Install and Set up kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl/)
+![prompt_img](img/screenshot-img.png)
 
-If using this with OpenShift, the oc tool needs installed.  It can be obtained from here:
+![prompt demo](img/kube-ps1.gif)
 
-[OC Client Tools](https://www.openshift.org/download.html)
+## Installing
 
-## Helper utilities
+### MacOS
 
-There are several great tools that make using kubectl very enjoyable.
+Homebrew package manager:
 
-[kubectx and kubenx](https://github.com/ahmetb/kubectx) are great for
-fast switching between clusters and namespaces.
+```
+$ brew update
+$ brew install kube-ps1
+```
+### From Source
 
-## Prompt Structure
+1. Clone this repository
+2. Source the kube-ps1.sh in your `~/.zshrc` or your `~/.bashrc`
 
-The prompt layout is:
+### Arch Linux
+AUR Package available at [https://aur.archlinux.org/packages/kube-ps1/](https://aur.archlinux.org/packages/kube-ps1/).
 
+#### Zsh
+```sh
+source /path/to/kube-ps1.sh
+PROMPT='$(kube_ps1)'$PROMPT
 ```
-(<symbol>|<cluster>:<namespace>)
+#### Bash
+```sh
+source /path/to/kube-ps1.sh
+PS1='[\u@\h \W $(kube_ps1)]\$ '
 ```
 
-## Enabling
+### Zsh Plugin Managers
 
-In order to use kube-ps1 with Oh My Zsh, you'll need to enable them in the
-.zshrc file. You'll find the zshrc file in your $HOME directory. Open it with
-your favorite text editor and you'll see a spot to list all the plugins you
-want to load.
+#### Using [zplugin](https://github.com/zdharma/zplugin)
 
-```shell
-vim $HOME/.zshrc
+Update `.zshrc` with:
+```sh
+zplugin light jonmosco/kube-ps1
+PROMPT='$(kube_ps1)'$PROMPT
 ```
 
-Add kube-ps1 to the list of enabled plugins and enable it on the prompt:
+## Requirements
 
-```shell
-plugins=(
-  git
-  kube-ps1
-)
+The default prompt assumes you have the `kubectl` command line utility installed.
+Official installation instructions and binaries are available:
 
-# After the "source Oh My Zsh" line
-PROMPT=$PROMPT'$(kube_ps1) '
-# Or in double quotes, don't forget to escape
-PROMPT=$PROMPT"\$(kube_ps1) "
+[Install and Set up kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl/)
+
+If using this with OpenShift, the `oc` tool needs installed.  It can be obtained
+from brew ports:
+
+```
+brew install openshift-cli
 ```
+or the source can be downloaded:
+
+[OC Client Tools](https://www.openshift.org/download.html)
 
-Note: The `PROMPT` example above was tested with the theme `robbyrussell`.
+Set the binary to `oc` with the following environment variable:
 
-## Enabling / Disabling on the current shell
+```
+KUBE_PS1_BINARY=oc
+```
 
-Sometimes the kubernetes information can be anoying, you can easily 
-switch it on and off with the following commands:
+If neither binary is available, the prompt will print the following:
 
-```shell
-kubeon
 ```
+(<symbol>|BINARY-N/A:N/A)
+```
+
+## Helper utilities
+
+There are several great tools that make using kubectl very enjoyable:
+
+- [`kubectx` and `kubens`](https://github.com/ahmetb/kubectx) are great for
+fast switching between clusters and namespaces.
+
+## Tmux port
+
+I have begun porting kube-ps1 to tmux as a status line plugin.  If you prefer
+tmux, and like the functionality provided by kube-ps1, checkout the
+[kube-tmux](https://github.com/jonmosco/kube-tmux) project
+
+## Prompt Structure
+
+The default prompt layout is:
 
-```shell
-kubeoff
+```
+(<symbol>|<context>:<namespace>)
 ```
 
-## Colors
+If the current-context is not set, kube-ps1 will return the following:
 
-Blue was used as the prefix to match the Kubernetes color as closely as
-possible. Red was chosen as the cluster name to stand out, and cyan
-for the namespace. Check the customization section for changing them.
+```
+(<symbol>|N/A:N/A)
+```
+
+## Enabling/Disabling
+
+If you want to stop showing Kubernetes status on your prompt string temporarily
+run `kubeoff`. To disable the prompt for all shell sessions, run `kubeoff -g`.
+You can enable it again in the current shell by running `kubeon`, and globally
+with `kubeon -g`.
+
+```
+kubeon     : turn on kube-ps1 status for this shell.  Takes precedence over
+             global setting for current session
+kubeon -g  : turn on kube-ps1 status globally
+kubeoff    : turn off kube-ps1 status for this shell. Takes precedence over
+             global setting for current session
+kubeoff -g : turn off kube-ps1 status globally
+```
 
 ## Customization
 
-The default settings can be overridden in ~/.zshrc
+The default settings can be overridden in `~/.bashrc` or `~/.zshrc` by setting
+the following environment variables:
 
 | Variable | Default | Meaning |
 | :------- | :-----: | ------- |
 | `KUBE_PS1_BINARY` | `kubectl` | Default Kubernetes binary |
+| `KUBE_PS1_NS_ENABLE` | `true` | Display the namespace. If set to `false`, this will also disable `KUBE_PS1_DIVIDER` |
 | `KUBE_PS1_PREFIX` | `(` | Prompt opening character  |
 | `KUBE_PS1_SYMBOL_ENABLE` | `true ` | Display the prompt Symbol. If set to `false`, this will also disable `KUBE_PS1_SEPARATOR` |
 | `KUBE_PS1_SYMBOL_DEFAULT` | `⎈ ` | Default prompt symbol. Unicode `\u2388` |
 | `KUBE_PS1_SYMBOL_USE_IMG` | `false` | ☸️  ,  Unicode `\u2638` as the prompt symbol |
-| `KUBE_PS1_NS_ENABLE` | `true` | Display the namespace. If set to `false`, this will also disable `KUBE_PS1_DIVIDER` |
-| `KUBE_PS1_SEPERATOR` | `\|` | Separator between symbol and cluster name |
-| `KUBE_PS1_DIVIDER` | `:` | Separator between cluster and namespace |
+| `KUBE_PS1_SEPARATOR` | &#124; | Separator between symbol and context name |
+| `KUBE_PS1_DIVIDER` | `:` | Separator between context and namespace |
 | `KUBE_PS1_SUFFIX` | `)` | Prompt closing character |
-| `KUBE_PS1_COLOR_SYMBOL` | `"%F{blue}"` | Custom color for the symbol |
-| `KUBE_PS1_COLOR_CONTEXT` | `"%F{red}"` | Custom color for the context |
-| `KUBE_PS1_COLOR_NS` | `"%F{cyan}"` | Custom color for the namespace |
-| `KUBE_PS1_ENABLED` | `true` | Set to false to start disabled on any new shell, `kubeon`/`kubeoff` will flip this value on the current shell |
+| `KUBE_PS1_CLUSTER_FUNCTION` | No default, must be user supplied | Function to customize how cluster is displayed |
+| `KUBE_PS1_NAMESPACE_FUNCTION` | No default, must be user supplied | Function to customize how namespace is displayed |
+
+For terminals that do not support UTF-8, the symbol will be replaced with the
+string `k8s`.
+
+To disable a feature, set it to an empty string:
+
+```
+KUBE_PS1_SEPARATOR=''
+```
+
+## Colors
+
+The default colors are set with the following environment variables:
+
+| Variable | Default | Meaning |
+| :------- | :-----: | ------- |
+| `KUBE_PS1_SYMBOL_COLOR` | `blue` | Set default color of the Kubernetes symbol |
+| `KUBE_PS1_CTX_COLOR` | `red` | Set default color of the context |
+| `KUBE_PS1_NS_COLOR` | `cyan` | Set default color of the namespace |
+| `KUBE_PS1_BG_COLOR` | `null` | Set default color of the prompt background |
+
+Blue was used for the default symbol to match the Kubernetes color as closely
+as possible. Red was chosen as the context name to stand out, and cyan for the
+namespace.
+
+Set the variable to an empty string if you do not want color for each
+prompt section:
+
+```
+KUBE_PS1_CTX_COLOR=''
+```
+
+Names are usable for the following colors:
+
+```
+black, red, green, yellow, blue, magenta, cyan
+```
+
+256 colors are available by specifying the numerical value as the variable
+argument.
+
+## Customize display of cluster name and namespace
+
+You can change how the cluster name and namespace are displayed using the
+`KUBE_PS1_CLUSTER_FUNCTION` and `KUBE_PS1_NAMESPACE_FUNCTION` variables
+respectively.
+
+For the following examples let's assume the following:
+
+cluster name: `sandbox.k8s.example.com`
+namespace: `alpha`
+
+If you're using domain style cluster names, your prompt will get quite long
+very quickly. Let's say you only want to display the first portion of the
+cluster name (`sandbox`), you could do that by adding the following:
+
+```sh
+function get_cluster_short() {
+  echo "$1" | cut -d . -f1
+}
+
+KUBE_PS1_CLUSTER_FUNCTION=get_cluster_short
+```
+
+The same pattern can be followed to customize the display of the namespace.
+Let's say you would prefer the namespace to be displayed in all uppercase
+(`ALPHA`), here's one way you could do that:
+
+```sh
+function get_namespace_upper() {
+    echo "$1" | tr '[:lower:]' '[:upper:]'
+}
+
+export KUBE_PS1_NAMESPACE_FUNCTION=get_namespace_upper
+```
+
+In both cases, the variable is set to the name of the function, and you must have defined the function in your shell configuration before kube_ps1 is called. The function must accept a single parameter and echo out the final value.
+
+### Bug Reports and shell configuration
+
+Due to the vast ways of customizing the shell, please try the prompt with a
+minimal configuration before submitting a bug report.
+
+This can be done as follows for each shell before loading kube-ps1:
+
+Bash:
+```bash
+bash --norc
+```
+
+Zsh:
+```bash
+zsh -f
+or
+zsh --no-rcs
+```
 
 ## Contributors
 
-- Jared Yanovich
-- Pedro Moranga
+* [Ahmet Alp Balkan](https://github.com/ahmetb)
+* Jared Yanovich