Add support for Ubuntu 20.04

README.md

@@ -35,7 +35,7 @@ The action works for all [GitHub-hosted runners](https://help.github.com/en/acti
 
 | Operating System | Versions |
 | ----------- | -------- |
-| Ubuntu  | `ubuntu-latest` (= `ubuntu-18.04`), `ubuntu-16.04` |
+| Ubuntu  | `ubuntu-20.04`, `ubuntu-latest` (= `ubuntu-18.04`), `ubuntu-16.04` |
 | macOS   | `macos-latest` |
 | Windows | `windows-latest` |
 

versions-strings-for-builder.rb

@@ -0,0 +1,15 @@
+hash = File.read('ruby-builder-versions.js')[/\bversions = {[^}]+}/]
+versions = eval hash
+
+by_minor = versions[:ruby].group_by { |v| v[/^\d\.\d/] }
+
+p by_minor['2.2']
+p by_minor['2.3']
+
+(4..7).each do |minor|
+  p by_minor["2.#{minor}"].map { |v| "ruby-#{v}" }
+end
+
+p (versions[:jruby] - %w[head]).map { |v| "jruby-#{v}" }
+
+p (versions[:truffleruby] - %w[head]).map { |v| "truffleruby-#{v}" }