feat(scoop-alter): Add scoop alter command to switch shim's target

[niheaven]

A WONDERFUL FEATURE OF SCOOP 😆 🎉

Description

Now Scoop could switch apps using scoop alter <app> just as (update-)alternatives in Linux. Meanwhile, uninstalling some apps which overwrite other's shims will restore previous ones (instead of removing commands).

• Instead of overwriting shims, Scoop renames original ones.
• During the uninstalling process, if there're renamed shims, Scoop will rename them back.
• Add new scoop alter command to choose default of command (a.k.a., shim)

Motivation and Context

There are many issues requesting this feature (just incomplete lists):

• Fixes Uninstall gow in main bucket also remove some features in coreutils. #4700
• Fixes Feature request: "namespacing" shims #1290
• Fixes Question: any way to prioritise shim sources? #3971
• Fixes Allow installing "lower priority" packages to skip shim overwrites #4253

How Has This Been Tested?

Tested in PowerShell 5.1/7.2.1, CMD, and WSL/Ubuntu. (Not tested in MSYS2 and CygWin)

Use 7zip/7zip-zstd and python/python3 as examples:

Uninstallation:

For command without alternatives:

For command without shim:

Checklist:

• I have read the Contributing Guide.
• I have updated the documentation accordingly.
• I have updated the tests accordingly.

[rashil2000]

Wow, very interesting!

Some notes:

• Since we are changing/refactoring function signatures, would it be good to follow PS conventions and call it Remove-Shim instead of rm_shim?
• In a subsequent PR, I might add a functionality to create user-defined shims, to solve Adding shims to an installation #3303. Since this is related to shims itself, should we call the file something other than scoop-alter.ps1?

[niheaven]

I'll make another PR that moves all shim-related functions to a separate file and refactors all the functions using PowerShell conventions, it's better IMO, right?

The 'user-defined shims' in #3303 is more likely links, it links a virtual app folder to some existing one and make new shims that points to them (likes scoop reset), have I misunderstood?

[rashil2000]

I'll make another PR that moves all shim-related functions to a separate file and refactors all the functions using PowerShell conventions, it's better IMO, right?

Sure.

The 'user-defined shims' in #3303 is more likely links, it links a virtual app folder to some existing one and make new shims that points to them (likes scoop reset), have I misunderstood?

No no, the idea is to allow creation of custom shims. For example, I want to create a shim like this:

scoop shim nvimdiff D:\Data\Scoop\apps\neovim\bin\nvim.exe -d

The nvimdiff shim is not created by the neovim manifest, but we can allow users to create custom shims like this. The format would be:

scoop shim <shim_name> <full_path_to_program> <arg1> <arg2> <arg3> ...

[niheaven]

Okay, got it.

scoop alter is more user-friendly IMO, end users needn't know what is 'shim' and they just alter the command. A specific command scoop shim for advanced users could add a subcommand that directly call it. scoop shim might have following subcommand:

• scoop shim <command> shows where the command comes from
  • likes scoop which, could call it directly or modify some output likes ' is from '
• scoop shim alter <command> calls scoop alter to change command's source
• scoop shim add <shim_name> <full_path_to_program> <arg1> <arg2> <arg3> ...
  • this is what you want
• scoop shim rm/del <command> remove shim
  • maybe give some caution notes?

[niheaven]

Any other suggestions? @rashil2000 @issaclin32

[rashil2000]

Yes, plan looks awesome!

But why create both scoop-alter and scoop-shim if scoop shim alter exist?

[niheaven]

Yes, plan looks awesome!

But why create both scoop-alter and scoop-shim if scoop shim alter exist?

For convenience 😆 . For example, in my use cases, I may never use scoop shim except for scoop shim alter if there is only scoop shim, and this is the general usage for most users IMO.

[rashil2000]

To be honest, the command scoop shim alter is more clear as to what exactly it is doing. scoop alter could mean anything (and not just shims). @issaclin32 thoughts?

[issaclin32]

I would vote for scoop shim alter. It looks more intuitive.

[niheaven]

This is not a binary choice; they are mutually inclusive. If only scoop shim alter is kept, I'll do some additional coding that adds basic functions of scoop shim.

[niheaven]

@rashil2000 I've done scoop shim command, but I prefer merge this PR and I'll submit a new one that accomplish the feature.