Install the self-contained binary version of pnpm

[zkochan]

This is a breaking change because the binary version of pnpm is only available from v6.17.1.
Also, it doesn't ship pnpx.

close #18

[KSXGitHub]

1. You intend to drop support for pnpm versions without self-contained binary, correct? If that's the case, why even bother running the self-installer and install it via the npm registry at all? Why not just download the binary directly from GitHub release?
2. Can you add code that check for unsupported pnpm versions before download? If user specify a pnpm version that doesn't have self-contained binary, it is more user-friendly to inform the user about it than an ambiguous 404.
3. Can you update the README.md file? Some information in README.md is ought to be outdated after this PR.
4. Finally, please remember to update dist/index.js before commit.

[KSXGitHub]

Amendment:

You intend to drop support for pnpm versions without self-contained binary, correct? If that's the case, why even bother running the self-installer and install it via the npm registry at all? Why not just download the binary directly from GitHub release?

GitHub Release does not support version ranges (e.g. ^6.17.1), so we must resolve to the correct version ourselves. Or just fallback to npm. Or drop support for version ranges entirely.

[KSXGitHub]

@zkochan When will you resolve my requests for change in this PR?

[zkochan]

I have to think about it. Not soon.

[privatenumber]

Curious if this would be easier to move forward with if it's opt-in via an option (eg. binary: true)?

[tksst]

I agree with @privatenumber .
Since this branch is very old and differs significantly from the latest master, I forked this action and implemented an option to install a self-contained binary.

I will post another PR after I add the test and update the readme.

[fz6m]

Good job @tksst .

I think adding a node-version option, detect it and auto switch pnpm@version to @pnpm/exe@version is better.

e.g.

jobs:
  build:
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        node-version: [14.x, 16.x, 18.x]
        os: [ubuntu-latest, windows-latest]
    steps:
      - name: Install pnpm
        uses: pnpm/action-setup@v3.0.0
        with:
          # in the node 14.x env, we auto install `@pnpm/exe` instead of `pnpm`
          # refer: https://pnpm.io/installation#compatibility
          node-version: ${{ matrix.node-version }}
          version: 8

      - name: Use Node.js ${{ matrix.node-version }}
        uses: actions/setup-node@v3
        with:
          node-version: ${{ matrix.node-version }}
          cache: 'pnpm'

[tksst]

@fz6m

I think adding a node-version option, detect it and auto switch pnpm@version to @pnpm/exe@version is better.

That is a nice feature, but a bit complicated.
I may try to implement it when I have time.

[tksst]

After thinking about how to implement this feature, I gave up trying to implement it.
The node-version option of setup-node can take various values. For example, "^18.0.0", ">=18.0.0", "lts/*", etc.
I need to implement the same logic to determine the version as actions/setup-node. This is difficult.