Release Dotty 0.21.0-RC1 and 0.20.0

[anatoliykmetyuk]

• Finalize the the stable and RC releases
  • Look at the milestone of the RC version being released. Move all the open issues from it to the next milestone.
  • Merge branch 0.20.x into master to guarantee that all of the 0.20.x commits are propagated to master
• Publish artifacts to Maven via CI. Use the following command: bash <(curl -sL https://raw.githubusercontent.com/lampepfl/dotty/master/docs/docs/contributing/release.sh) 20
  • On branch 0.20.x, set baseVersion to 0.20.0 and git tag it as 0.20.0. This will publish artefacts to Sonatype and GitHub Release
  • Create branch 0.21.x from master
  • On 0.21.x, set baseVersion to 0.21.0-RC1 and git tag it as 0.21.0-RC1. This will publish artefacts to Sonatype and GitHub Release.
  • On master, set baseVersion to 0.22.0
• Update scalaVersion (and, if applicable, the sbt-dotty version) in the Dotty ecosystem projects
  • https://github.com/lampepfl/dotty-example-project
    • Committed to master
  • https://github.com/lampepfl/dotty-example-project/tree/mill
  • https://github.com/lampepfl/dotty.g8
    • Committed to master
  • https://github.com/lampepfl/dotty-cross.g8
    • Committed to master
  • https://github.com/lampepfl/dotty-staging.g8
    • Committed to master
  • https://github.com/lampepfl/homebrew-brew
    • Committed to master
    • SHA256 sum for the artifact: wget -q -O- https://github.com/lampepfl/dotty/releases/download/0.21.0-RC1/sha256sum.txt | grep ".tar.gz"
  • https://github.com/lampepfl/packtest
    • Committed to master
  • https://github.com/lampepfl/xml-interpolator
    • PR submitted
    • PR merged
  • https://github.com/scalacenter/scastie
    • PR submitted
    • PR merged
    • https://scastie.scala-lang.org/ -> Build Settings -> Dotty mentions 0.21.0-RC1
  • Dotty reference compiler
    • PR submitted
    • PR merged
  • Scalac
    • PR submitted
    • PR merged
• Announce the release
  • Publish releases for the RC and stable versions on GitHub Releases
  • Publish Blog Post on dotty.epfl.ch
  • Make an announcement thread on https://contributors.scala-lang.org
  • Tweet the announcement blog post on https://twitter.com/scala_lang

Instructions on how to release