Supress warning issued for redirect pages (#8347)

Merge pull request 8347

features/permalinks.feature

@@ -151,3 +151,20 @@ Feature: Fancy permalinks
     And the _site directory should exist
     And I should see "Conflict: The URL '" in the build output
     And I should see "amazing.html' is the destination for the following pages: awesome.md, cool.md" in the build output
+
+  Scenario: Redirecting from an existing permalink
+    Given I have a configuration file with "plugins" set to "[jekyll-redirect-from]"
+    And I have a "deals.html" file with content:
+      """
+      ---
+      permalink: /deals/
+      redirect_from:
+        - /offers/
+      ---
+      """
+    And I have a "offers.html" page with permalink "/offers/" that contains "Hurry! Limited time only!"
+    When I run jekyll build
+    Then I should get a zero exit status
+    And the _site directory should exist
+    And I should not see "Conflict: The URL '" in the build output
+    And I should not see "offers/index.html' is the destination for the following pages: offers.html, redirect.html" in the build output

lib/jekyll/commands/doctor.rb

@@ -124,6 +124,8 @@ module Jekyll
 
         def collect_urls(urls, things, destination)
           things.each do |thing|
+            next if allow_used_permalink?(thing)
+
             dest = thing.destination(destination)
             if urls[dest]
               urls[dest] << thing.path
@@ -134,6 +136,10 @@ module Jekyll
           urls
         end
 
+        def allow_used_permalink?(item)
+          defined?(JekyllRedirectFrom) && item.is_a?(JekyllRedirectFrom::RedirectPage)
+        end
+
         def case_insensitive_urls(things, destination)
           things.each_with_object({}) do |thing, memo|
             dest = thing.destination(destination)