(maint) Make builds reproducible

When the standard SOURCE_DATE_EPOCH environment variable is set, this
patch causes the default certificate name and manpages to become
deterministic, helping the reproducibility of Puppet builds.

This patch has been in use in the Debian packaging of Puppet for some
time, without issue.

Author: lamby

tasks/manpages.rake

@@ -13,6 +13,11 @@ task :gen_manpages do
 
   ronn_args = '--manual="Puppet manual" --organization="Puppet, Inc." --roff'
 
+  unless ENV['SOURCE_DATE_EPOCH'].nil?
+    source_date = Time.at(ENV['SOURCE_DATE_EPOCH'].to_i).strftime('%Y-%m-%d')
+    ronn_args += " --date=#{source_date}"
+  end
+
   # Locate ronn
   begin
     require 'ronn'