Support shell auto-completion

[t1m0thyj]

Is your feature or enhancement request related to a problem or limitation? Please describe

I wish that Tab auto-completion would be supported by Zowe CLI in popular shells like Bash and Zsh.

Describe your enhancement idea

Enable autocompletion in Zowe CLI with the yargs.completion API, which enables a zowe completion command to generate a shell script that can be added to ~/.bashrc or ~/.zshrc: https://yargs.js.org/docs/#api-reference-completioncmd-description-fn

Describe alternatives you've considered

I can launch web help to see command syntax, but this requires switching to a browser and is less context sensitive.

Provide any additional context

The configuration of Yargs for Zowe CLI happens in the YargsConfigurer class.

On MacOS the script generated by Yargs looks like this:

#compdef zowe
###-begin-zowe-completions-###
#
# yargs command completion script
#
# Installation: zowe completion >> ~/.zshrc
#    or zowe completion >> ~/.zprofile on OSX.
#
_zowe_yargs_completions()
{
  local reply
  local si=$IFS
  IFS=$'
' reply=($(COMP_CWORD="$((CURRENT-1))" COMP_LINE="$BUFFER" COMP_POINT="$CURSOR" zowe --get-yargs-completions "${words[@]}"))
  IFS=$si
  _describe 'values' reply
}
compdef _zowe_yargs_completions zowe
###-end-zowe-completions-###

Note: The built-in autocompletion provided by Yargs works pretty well, but we may need to customize the yargs.completion handler to extract only the first line out of command descriptions, because multiple lines seem to mess it up.

[github-actions]

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[traeok]

Support for PowerShell is an open feature request for yargs: yargs/yargs#1290