Make Strategy#page_headers more general purpose

Library/Homebrew/livecheck/strategy.rb

@@ -86,7 +86,7 @@ module Homebrew
 
         return @headers[url] if @headers.key?(url)
 
-        headers = {}
+        headers = []
 
         [:default, :browser].each do |user_agent|
           stdout, _, status = curl_output(
@@ -99,9 +99,9 @@ module Homebrew
           while stdout.match?(/\AHTTP.*\r$/)
             h, stdout = stdout.split("\r\n\r\n", 2)
 
-            headers = headers.merge(h.split("\r\n").drop(1)
+            headers << h.split("\r\n").drop(1)
                         .map { |header| header.split(/:\s*/, 2) }
-              .to_h.transform_keys(&:downcase))
+                        .to_h.transform_keys(&:downcase)
           end
 
           return (@headers[url] = headers) if status.success?

Library/Homebrew/livecheck/strategy/header_match.rb

@@ -36,12 +36,16 @@ module Homebrew
 
           headers = Strategy.page_headers(url)
 
+          # Merge the headers from all responses into one hash
+          merged_headers = {}
+          headers.each { |resp_headers| merged_headers.merge!(resp_headers) }
+
           if block
-            match = block.call(headers)
+            match = block.call(merged_headers)
           else
             match = nil
 
-            if (filename = headers["content-disposition"])
+            if (filename = merged_headers["content-disposition"])
               if regex
                 match ||= location[regex, 1]
               else
@@ -50,7 +54,7 @@ module Homebrew
               end
             end
 
-            if (location = headers["location"])
+            if (location = merged_headers["location"])
               if regex
                 match ||= location[regex, 1]
               else