release.yml: Fix tag conversion for Ruby 4.0

and PREVIOUS_RELEASE_TAG for any .0 releases

.github/workflows/release.yml

@@ -49,9 +49,9 @@ jobs:
 
       - name: Create a release on GitHub
         run: |
-          RELEASE_TAG=$(echo v${{ env.RUBY_VERSION }} | sed 's/\./_/g')
+          RELEASE_TAG=$(ruby tool/ruby-version.rb tag "${{ env.RUBY_VERSION }}")
           echo $RELEASE_TAG
-          PREVIOUS_RELEASE_TAG=$(echo $RELEASE_TAG | awk 'BEGIN {FS="_"; OFS="_"}{ $NF=$NF-1; print }')
+          PREVIOUS_RELEASE_TAG=$(ruby tool/ruby-version.rb previous-tag "${{ env.RUBY_VERSION }}")
           echo $PREVIOUS_RELEASE_TAG
           tool/gen-github-release.rb $PREVIOUS_RELEASE_TAG $RELEASE_TAG --no-dry-run
         env:

tool/ruby-version.rb

@@ -1,3 +1,5 @@
+#!/usr/bin/env ruby
+
 module RubyVersion
   def self.tag(version)
     major_version = Integer(version.split('.', 2)[0])
@@ -35,3 +37,16 @@ module RubyVersion
     end
   end
 end
+
+if __FILE__ == $0
+  case ARGV[0]
+  when "tag"
+    print RubyVersion.tag(ARGV[1])
+  when "previous"
+    print RubyVersion.previous(ARGV[1])
+  when "previous-tag"
+    print RubyVersion.tag(RubyVersion.previous(ARGV[1]))
+  else
+    "#{$0}: unexpected command #{ARGV[0].inspect}"
+  end
+end