How to run yarn install on CI without --immutable #3485
Description
We run yarn install on CI, and it fails with https://yarnpkg.com/advanced/error-codes#yn0028---frozen_lockfile_exception.
We'd rather avoid committing yarn.lock, because tests are running against latest yarn berry version and this might imply updating yarn.lock. Actually, we don't need exact installed package versions, so no real need in yarn.lock.
The tests are running on TeamCity CI. As I can see, --immutable is implied if CI or TEAMCITY_VERSION environment variables are set. Unfortunately, it's not enough. Could you please point me out to code that calculates --immutable default value?