deprecate(old_usage, new_usage, call_site)
Warn about deprecated usage.
Example:
Rake.application.deprecate("import", "Rake.import", caller.first)
# File lib/rake/application.rb, line 165 def deprecate(old_usage, new_usage, call_site) return if options.ignore_deprecate $stderr.puts "WARNING: '#{old_usage}' is deprecated. " + "Please use '#{new_usage}' instead.\n" + " at #{call_site}" end