From adce349d7a7a0754cb16b1064a7e96b6e26613ac Mon Sep 17 00:00:00 2001
From: Nicholas Burlett <nickburlett@mac.com>
Date: Wed, 18 Mar 2015 10:18:37 -0700
Subject: [PATCH 1/3] Clear the regenerator cache every time we process

To address part of #3591, clear the regenerator's cache every time the
site is processed. This ensures that the regenerator doesn't incorrectly
believe a file hasn't changed based on stale information.
---
 lib/jekyll/regenerator.rb | 8 ++++++++
 lib/jekyll/site.rb        | 1 +
 2 files changed, 9 insertions(+)

diff --git a/lib/jekyll/regenerator.rb b/lib/jekyll/regenerator.rb
index 0616fdd9..b829a95c 100644
--- a/lib/jekyll/regenerator.rb
+++ b/lib/jekyll/regenerator.rb
@@ -59,6 +59,14 @@ module Jekyll
       @cache = {}
     end
 
+
+    # Clear just the cache
+    #
+    # Returns nothing
+    def clear_cache
+      @cache = {}
+    end
+
     # Checks if a path's (or one of its dependencies)
     # mtime has changed
     #
diff --git a/lib/jekyll/site.rb b/lib/jekyll/site.rb
index 96910255..3961669a 100644
--- a/lib/jekyll/site.rb
+++ b/lib/jekyll/site.rb
@@ -68,6 +68,7 @@ module Jekyll
       self.static_files = []
       self.data = {}
       @collections = nil
+      @regenerator.clear_cache()
 
       if limit_posts < 0
         raise ArgumentError, "limit_posts must be a non-negative number"

From 15ebf929e107d430fa32ca5301ed176c44995478 Mon Sep 17 00:00:00 2001
From: Nicholas Burlett <nickburlett@mac.com>
Date: Wed, 18 Mar 2015 22:30:31 -0700
Subject: [PATCH 2/3] Use the new clear_cache method

Instead of assigning `@cache = {}`, clear the cache using `clear_cache`
---
 lib/jekyll/regenerator.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/jekyll/regenerator.rb b/lib/jekyll/regenerator.rb
index b829a95c..76d720af 100644
--- a/lib/jekyll/regenerator.rb
+++ b/lib/jekyll/regenerator.rb
@@ -9,7 +9,7 @@ module Jekyll
       read_metadata
 
       # Initialize cache to an empty hash
-      @cache = {}
+      clear_cache
     end
 
     # Checks if a renderable object needs to be regenerated
@@ -56,7 +56,7 @@ module Jekyll
     # Returns nothing
     def clear
       @metadata = {}
-      @cache = {}
+      clear_cache
     end
 
 

From e770a080a7af3f379014dde1436e150edc967e44 Mon Sep 17 00:00:00 2001
From: Nicholas Burlett <nickburlett@mac.com>
Date: Thu, 19 Mar 2015 09:41:05 -0700
Subject: [PATCH 3/3] Regenerator cache clearing tests

Two tests for the regenerator cache clearing changes:

1. Intrusively test that the regnerator.clear_cache actually clears the cache ( in test/test_regenerator.rb )
2. Test that incremental building regenerates files that have changed that previously were unchanged ( in test/test_site.rb )
---
 test/test_regenerator.rb |  9 +++++++++
 test/test_site.rb        | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/test/test_regenerator.rb b/test/test_regenerator.rb
index 15819487..87312333 100644
--- a/test/test_regenerator.rb
+++ b/test/test_regenerator.rb
@@ -75,6 +75,15 @@ class TestRegenerator < JekyllUnitTest
       assert @regenerator.cache[@path]
     end
 
+    should "clear the cache on clear_cache" do
+      # @path will be in the cache because the
+      # site will have processed it
+      assert @regenerator.cache[@path]
+
+      @regenerator.clear_cache
+      assert_equal  @regenerator.cache, {}
+    end
+
     should "write to the metadata file" do
       @regenerator.clear
       @regenerator.add(@path)
diff --git a/test/test_site.rb b/test/test_site.rb
index 4bc7ddb2..7888f330 100644
--- a/test/test_site.rb
+++ b/test/test_site.rb
@@ -459,5 +459,43 @@ class TestSite < JekyllUnitTest
       end
     end
 
+    context "incremental build" do
+      setup do
+        @site = Site.new(site_configuration({
+          'full_rebuild' => false
+        }))
+        @site.read
+      end
+
+      should "build incrementally" do
+        contacts_html = @site.pages.find { |p| p.name == "contacts.html" }
+        @site.process
+
+        source = @site.in_source_dir(contacts_html.path)
+        dest = File.expand_path(contacts_html.destination(@site.dest))
+        mtime1 = File.stat(dest).mtime.to_i # first run must generate dest file
+
+        # need to sleep because filesystem timestamps have best resolution in seconds
+        sleep 1
+        @site.process
+        mtime2 = File.stat(dest).mtime.to_i
+        assert_equal mtime1, mtime2 # no modifications, so remain the same
+
+        # simulate file modification by user
+        FileUtils.touch source
+
+        sleep 1
+        @site.process
+        mtime3 = File.stat(dest).mtime.to_i
+        refute_equal mtime2, mtime3 # must be regenerated 
+
+        sleep 1
+        @site.process
+        mtime4 = File.stat(dest).mtime.to_i
+        assert_equal mtime3, mtime4 # no modifications, so remain the same
+      end
+
+    end
+
   end
 end