Add MSpec tool to automatically wrap spec files with a guard

spec/mspec/tool/wrap_with_guard.rb

@@ -0,0 +1,28 @@
+#!/usr/bin/env ruby
+# Wrap the passed the files with a guard (e.g., `ruby_version_is ""..."3.0"`).
+# Notably if some methods are removed, this is a convenient way to skip such file from a given version.
+# Example usage:
+# $ spec/mspec/tool/wrap_with_guard.rb 'ruby_version_is ""..."3.0"' spec/ruby/library/set/sortedset/**/*_spec.rb
+
+guard, *files = ARGV
+abort "Usage: #{$0} GUARD FILES..." if files.empty?
+
+files.each do |file|
+  contents = File.binread(file)
+  lines = contents.lines.to_a
+
+  lines = lines.map { |line| line.chomp.empty? ? line : "  #{line}" }
+
+  version_line = "#{guard} do\n"
+  if lines[0] =~ /^\s*require.+spec_helper/
+    lines[0] = lines[0].sub(/^  /, '')
+    lines.insert 1, "\n", version_line
+  else
+    warn "Could not find 'require spec_helper' line in #{file}"
+    lines.insert 0, version_line
+  end
+
+  lines << "end\n"
+
+  File.binwrite file, lines.join
+end