From f2263a11b73091f0b94b8c6fe6f467e0a96b2d3d Mon Sep 17 00:00:00 2001
From: Parker Moore <parkrmoore@gmail.com>
Date: Mon, 4 Apr 2016 11:49:24 -0700
Subject: [PATCH] Only write collections.posts.permalink if permalink is set.

---
 lib/jekyll/configuration.rb | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/jekyll/configuration.rb b/lib/jekyll/configuration.rb
index 87bfeb46..5b5bb2df 100644
--- a/lib/jekyll/configuration.rb
+++ b/lib/jekyll/configuration.rb
@@ -72,7 +72,7 @@ module Jekyll
         'hard_wrap'      => false,
         'footnote_nr'    => 1
       }
-    }]
+    }].freeze
 
     # Public: Turn all keys into string
     #
@@ -271,14 +271,20 @@ module Jekyll
     def add_default_collections
       config = clone
 
+      # It defaults to `{}`, so this is only if someone sets it to null manually.
       return config if config['collections'].nil?
 
+      # Ensure we have a hash.
       if config['collections'].is_a?(Array)
         config['collections'] = Hash[config['collections'].map { |c| [c, {}] }]
       end
+
+      # Add posts.
       config['collections']['posts'] ||= {}
       config['collections']['posts']['output'] = true
-      config['collections']['posts']['permalink'] = style_to_permalink(config['permalink'])
+      if config['permalink']
+        config['collections']['posts']['permalink'] ||= style_to_permalink(config['permalink'])
+      end
 
       config
     end