add command line interface for this gem

datadog-ci.gemspec

@@ -23,6 +23,9 @@ Gem::Specification.new do |spec|
   spec.homepage = "https://github.com/DataDog/datadog-ci-rb"
   spec.license = "BSD-3-Clause"
 
+  spec.bindir = "exe"
+  spec.executables = ["ddcirb"]
+
   spec.metadata["allowed_push_host"] = "https://rubygems.org"
   spec.metadata["changelog_uri"] = "https://github.com/DataDog/datadog-ci-rb/blob/main/CHANGELOG.md"
   spec.metadata["homepage_uri"] = spec.homepage
@@ -36,6 +39,7 @@ Gem::Specification.new do |spec|
       README.md
       ext/**/*
       lib/**/*
+      exe/**/*
     ]].select { |fn| File.file?(fn) } # We don't want directories, only files
       .reject { |fn| fn.end_with?(".so", ".bundle") } # Exclude local native binary artifacts
 

exe/ddcirb

@@ -0,0 +1,28 @@
+#!/usr/bin/env ruby
+
+require "rspec/core"
+require "datadog/ci"
+
+Datadog.configure do |c|
+  c.ci.enabled = true
+  c.ci.itr_enabled = true
+  c.ci.discard_traces = true
+  c.ci.instrument :rspec, dry_run_enabled: true
+  c.tracing.enabled = true
+end
+
+rspec_cli_options = %w[
+  --dry-run
+  spec
+]
+
+options = ::RSpec::Core::ConfigurationOptions.new(rspec_cli_options)
+devnull = File.new("/dev/null", "w")
+exit_code = ::RSpec::Core::Runner.new(options).run(devnull, devnull)
+
+if exit_code != 0
+  Datadog.logger.error("RSpec dry-run failed with exit code #{exit_code}")
+end
+
+test_optimisation = Datadog.send(:components).test_optimisation
+print((test_optimisation.skipped_tests_count.to_f / test_optimisation.total_tests_count).floor(2))