How To Get Commit Hashes

Checkout or download any revision of swift repo
Create empty folder and put swift repo there, for example to ~/ws/swift-checkout/swift-5.7-RELEASE.
Check file utils/update_checkout/update-checkout-config.json, look for repos.branch-schemes.<release-version>, copy needed hashes from it.
Replace updateChekcoutOutput from DefaultRevisionsMap.swift with output of utils/update-checkout
Update some repo names, so they are equal to Checkoutable.repoName.
Update checkout tag for swift repo itself. Search for struct SwiftRepo
Some repos not not in update-checkout-config.json, like curl ot libxml, keep them while it is working

This process take some time, but ideally needed only once per release

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