Run CI against minimum supported Sorbet version

Extract minimum Sorbet version from gemspec and run against that to make
sure we're actually compatible.

Author: sambostock

.github/workflows/ci.yml

@@ -39,6 +39,7 @@ jobs:
           - Gemfile
           - gemfiles/Gemfile-rails-6-1
           - gemfiles/Gemfile-rails-main
+          - gemfiles/Gemfile-sorbet-minimum
         include:
           - gemfile: gemfiles/Gemfile-rails-main
             experimental: true

gemfiles/Gemfile-sorbet-minimum

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+# Extract minimum supported version from gemspec
+minimum_sorbet_version = File.read("tapioca.gemspec")[
+  # spec.add_dependency("sorbet-static-and-runtime", ">= 1.2.3456")
+  #                                                      ^^^^^^^^
+  /"sorbet-static-and-runtime", ">= ([^"]+)"/,
+  1,
+]
+
+gem("sorbet-static-and-runtime", minimum_sorbet_version)
+
+eval_gemfile "../Gemfile"