Disables auto-pinning by default

[arcanis]

I believe Corepack shouldn't have any negative impact on projects that aren't configured to use it. It should only be a net positive. Changing a file from the project has negative impacts as it leads to confusion ("why is this file changing?"), frustration ("I need to revert the file after every command!"), and sometimes breakages (pristine checks).

I didn't object much to auto-pinning at the time it was introduced because it was a request made by people from the TSC, and I was interested in compromise seeking. Considering the TSC declined to push Corepack further, I see less value in that and I'd like to revisit this design.

Fixes #485

Closes #552

[aduh95]

Duplicate of #552?

[arcanis]

Duplicate of #552?

I didn't see it before but yeah, same intent. It supersedes it though; it also updates the tests.

[MikeMcC399]

I would appreciate this PR moving forward!

Just yesterday I had to ask somebody to revert a commit because they had accidently added a Yarn Classic packageManager to a repo that uses npm as package manager.

Removing the default auto-pinning would help prevent these sorts of mistakes.

[trivikr]

LGTM. Waiting to see it in newer version of corepack, taking it more close to 1.0.0

[crazyair]

How to subscribe to publishing new versions? I want to upgrade as soon as possible

[friederbluemle]

Thank you so much for merging and releasing this. It was driving me nuts that corepack was polluting my legacy Yarn 1 repos by forcibly adding a packageManager in package.json.

[MikeMcC399]

It's been merged into v0.33.0 and the process to roll it out through Node.js bundling has begun. Node.js 24.2.0 has already picked it up, for instance.