Yarn tries to create shims of shims during global package installation

[ArcanoxDragon]

Related to #6902

The update to @zkochan/cmd-shim@3.0.0 in yarn@1.13.0 revealed a dormant bug where Yarn calls cmd-shim on its own shims, creating shims of shims which do not function correctly in PowerShell. This issue mainly affects Windows, although creating shims of shims in Linux is probably not the greatest solution when the original shim could be used instead.

This issue is intended to track the underlying cause of this, and, eventually, a real fix that can replace the workaround in #6954 and allow proper PowerShell shims to be used.

[tats-u]

Thank you for creating this issue on behalf of me.

Additional info:

• yarn/src/cli/commands/global.js

  Lines 169 to 171 in 1af4c5f

  	if (process.platform === 'win32' && dest.indexOf('.cmd') !== -1) {
  	await fs.rename(dest + '.cmd', dest);
  	}

  camouflaged this issue before 1.12.3.
• How to fix:
  1. Make @zkochan/cmd-shim support shims of shims
  2. Stop creating shims of shims (Use alternate method of generating global bin shims #6959)

[ExE-Boss]

i. Make @zkochan/cmd-shim support shims of shims

I don't think that's a real solution.

That's just a band-aid for a band-aid.

---

/cc @zkochan

[tats-u]

Shims mean symlinks made of shell scripts. Since symlink supports nested links, shims also must do.
Or cmd-shim MUST CLARIFY that it doesn't.