(#310, #3318) Add Uninstall-ChocolateyPath cmdlet & rewrite associated functions as cmdlets

[vexx32]

Description Of Changes

• Added Uninstall-ChocolateyPath helper cmdlet
• Rewrote the following associated functions into C# cmdlets:
  • Get-EnvironmentVariable
  • Get-EnvironmentVariableNames
  • Install-ChocolateyPath
  • Set-EnvironmentVariable
  • Test-ProcessAdminRights
  • Update-SessionEnvironment
• Tweaked the PowerShell command lookup behaviour when loading the chocolateyInstaller.psm1 module to ensure that licensed cmdlets can be preferentially used instead of open-source cmdlets or functions, regardless of any name collisions that may occur.
• Tweaked the assembly resolver to ensure that if we have the licensed extension depend on the new Chocolatey.PowerShell assembly, it will not cause any issues when trying to load the licensed extension outside the PowerShell module context.
• Added an update-cmdlet-documentation.ps1 script which will use PlatyPS to read the cmdlet metadata and keep documentation up to date.
  • Provides a -NewCommand switch to allow easier additions of documentation pages for any new cmdlets (PlatyPS does not add newly added commands by default).
  • This script directly adds or updates documentation in a local copy of the chocolatey/docs repository, and compiles an XML help file from the resulting content.

Motivation and Context

Partially, we just want to finally add Uninstall-ChocolateyPath. However, given overall contribution rates to the powershell functions are quite low, the decision has been made to rewrite our helper functions into C# cmdlets.

This PR serves as the initial set of cmdlets, a handful of useful example cases to prove out the viability of this approach, as well as ensuring that we have a better path forward for both OSS commands and any licensed commands we want to use in the future. It also opens up the possibility of more easily overriding the OSS cmdlets with a licensed command, and there are provisions in the chocolateyInstaller.psm1 module script to ensure that can work seamlessly.

Testing

1. Using the add-path.zip package (renamed to .nupkg), attempt to install and uninstall the package running the chocolatey.console project in Visual Studio, specifying package parameters as /Path=C:\test /Scope=Machine (or other paths, or with /Scope=User).
2. Build the project to completion and install the resulting package on a VM. Run the same test on this VM.
3. Copy the installation of Chocolatey here to a folder that does not require administrative access, set $env:ChocolateyInstall to this folder, and attempt to run the same tests as before with the choco.exe in this folder. You should notice that any attempts to write to the Machine scope path fail with an error.
4. In a PowerShell session, import the chocolatey installer module Import-Module $env:ChocolateyInstall/helpers/chocolateyInstaller.psm1 and check the Get-Help results for Install-ChocolateyPath, Uninstall-ChocolateyPath, and the other provided cmdlets. None of the cmdlets added/rewritten here should be missing help.

There will be a related PR to the licensed extension repository with some additional instructions to confirm the command overriding behaviour works and inheritance from this new assembly can function correctly.

For documentation generation:

1. Ensure you have the chocolatey/docs repository cloned locally. (use the branch from this draft docs PR: (doc) Add/update docs for Chocolatey.PowerShell module docs#993)
2. Run the provided update-cmdlet-documentation.ps1 script, optionally providing the path to the docs repo folder with -DocsRepositoryPath if it is cloned in a folder that is not ../docs relative to the choco repository.

For the present I have included the XML rendition of the help in the repository, and I think it makes sufficient sense to just update this file whenever we need to; the markdown help can remain in the docs repository, and updating the XML help for this PowerShell module can be done as-needed and just committed to this repository.

The Invoke-Tests.ps1 file should also run the included Pester tests for these commands.

Operating Systems Testing

Win10

Change Types Made

• Bug fix (non-breaking change).
• Feature / Enhancement (non-breaking change).
• Breaking change (fix or feature that could cause existing functionality to change).
• Documentation changes.
• PowerShell code changes.

Change Checklist

• Requires a change to the documentation.
• Documentation has been updated.
• Tests to cover my changes, have been added.
• All new and existing tests passed?

Related Issue

Fixes #310

Fixes #3318

[AdmiringWorm]

Great work on this @vexx32. @gep13 asked me to have an additional look over the changes, and comment if I noticed anything.

[gep13]

@vexx32 one other thing that I thought about yesterday, but didn't mention...

Can you update your commit messages to provide more information? If/when reviewing the commits directly, we won't have the same context that exists in this PR. I am thinking that all the information in the PR description should make its way into the commit messages.

Thoughts?

[vexx32]

That sounds like rather a lot, but I don't disagree, I'll look to do that too.

EDIT: Done.

[gep13]

@vexx32 can you let me know when the last remaining unresolved comments have been worked on? I would like to get this merged, so that we can continue with testing. Thanks

NOTE: I will mention here again, I forced pushed this PR on the head of develop, as I thought that it was ready for merging. You will need to reset you clone before continuing.

[vexx32]

@gep13 I think I have everything sorted out, apologies for the wait on the last little bits here. :3

[gep13]

LGTM!

The requested changes have been completed.

[gep13]

@vexx32 thank you very much for your work on this! It is great to see this getting added!