Update the pinned pnpm version for Volta

[oscard0m]

What would you like Renovate to be able to do?

Currently, renovate will update the pinned versions of yarn, node and npm in the volta key. Is it possible to also support updating the pinned pnpm version?

Even though pnpm for Volta is experimental, I think it's safe to support it.

Did you already have any implementation ideas?

I assume it would be a matter of adding an extra check in lib/modules/manager/npm/extract/index.ts:

if (depType === 'volta') {
   if (depName === 'node') {
     dep.datasource = GithubTagsDatasource.id;
     dep.packageName = 'nodejs/node';
     dep.versioning = nodeVersioning.id;
   } else if (depName === 'yarn') {
     dep.datasource = NpmDatasource.id;
     dep.commitMessageTopic = 'Yarn';
     const major =
       isVersion(dep.currentValue) && api.getMajor(dep.currentValue);
     if (major && major > 1) {
       dep.packageName = '@yarnpkg/cli';
     }
   } else if (depName === 'npm') {
     dep.datasource = NpmDatasource.id;
+  } else if (depName === 'pnpm') {
+    dep.datasource = NpmDatasource.id;
+    dep.commitMessageTopic = 'pnpm';
   } else {
     dep.skipReason = 'unknown-volta';
   }
   if (!isValid(dep.currentValue)) {
     dep.skipReason = 'unspecified-version';
   }
   return dep;
}

And updating the corresponding test and snapshot.

I'm happy to open a PR for this once you validate this makes sense.

[rarkins]

PR welcome!