Fix improperly configured host in generated urls

If the host in `default_url_options` is accidentally set with a protocol such as 

```
host: "http://example.com"
``` 

then the generated url will have the protocol twice `http://http://example.com` which is not what the user intended. Likely they wanted to define a host `host: "example.com"` and a `protocol: "http://"` but did not know the convention.

This may not the most common problem, but when it happens it can go undetected for a while. I accidentally added `http://` out of habit recently only to find all the links in my emails were broken after deploying a demo site to production. Rather than allow this accident go undetected, we can fix the problem in line by properly setting the protocol and host.


I was able to find this related question on stack overflow: http://stackoverflow.com/questions/5878329/rails-3-devise-how-do-i-make-the-email-confirmation-links-use-secure-https-n where the answer was highly upvoted.

This is based off of work in rails#7415 cc/ @pixeltrix

back port of rails#9794

ATP Action Mailer and Action Pack

actionpack/CHANGELOG.md

@@ -1,5 +1,13 @@
 ## unreleased ##
 
+*   Allow default url options to accept host with protocol such as `http://`
+
+        config.action_mailer.default_url_options = { host: "http://mydomain.com" }
+
+    Backport #9794
+
+    *Richard Schneeman*
+
 *   `ActiveSupport::NumberHelper#number_to_human` returns the number unaltered when
     the units hash does not contain the needed key, e.g. when the number provided is less
     than the largest key proivided.

actionpack/lib/action_dispatch/http/url.rb

@@ -28,8 +28,9 @@ def url_for(options = {})
           rewritten_url = ""
 
           unless options[:only_path]
+            protocol = extract_protocol(options)
             unless options[:protocol] == false
-              rewritten_url << (options[:protocol] || "http")
+              rewritten_url << protocol
               rewritten_url << ":" unless rewritten_url.match(%r{:|//})
             end
             rewritten_url << "//" unless rewritten_url.match("//")
@@ -67,6 +68,16 @@ def rewrite_authentication(options)
           end
         end
 
+        # Extracts protocol http:// or https:// from options[:host]
+        # needs to be called whether the :protocol is being used or not
+        def extract_protocol(options)
+          if options[:host] && match = options[:host].match(/(^.*:\/\/)(.*)/)
+            options[:protocol] ||= match[1]
+            options[:host]     =   match[2]
+          end
+          options[:protocol] || "http"
+        end
+
         def host_or_subdomain_and_domain(options)
           return options[:host] if !named_host?(options[:host]) || (options[:subdomain].nil? && options[:domain].nil?)
 

actionpack/test/dispatch/url_generation_test.rb

@@ -39,6 +39,14 @@ def app
       https!
       assert_equal "http://www.example.com/foo", foo_url(:protocol => "http")
     end
+
+    test "extracting protocol from host when protocol not present" do
+      assert_equal "httpz://www.example.com/foo", foo_url(host: "httpz://www.example.com", protocol: nil)
+    end
+
+    test "formatting host when protocol is present" do
+      assert_equal "http://www.example.com/foo", foo_url(host: "httpz://www.example.com", protocol: "http://")
+    end
   end
 end