Improve Windows packaging experience

Previously, when the DownloadCache was used on a Windows machine, it
could not read and write files properly.  This was due to it using the
default system encoding which differed from the expected UTF-8.  This
change updates the DownloadCache to always read and write files as
binary in order to get around the encoding issue.

Previously, when files were cached by the DownloadCache, the file
names were escaped to ensure that there were no forward slashes in
them.  On Windows, this escaping is not sufficient, as colons must be
escaped as well.  This change updates the escaping to cover this
additional case.

[#71925232][resolves #53]

Author: nebhale

lib/java_buildpack/util/cache/cached_file.rb

@@ -34,7 +34,7 @@ class CachedFile
         def initialize(cache_root, uri)
           FileUtils.mkdir_p cache_root
 
-          key            = URI.escape(uri, '/')
+          key            = URI.escape(uri, ':/')
           @cached        = cache_root + "#{key}.cached"
           @etag          = cache_root + "#{key}.etag"
           @last_modified = cache_root + "#{key}.last_modified"

lib/java_buildpack/util/cache/download_cache.rb

@@ -63,7 +63,7 @@ def get(uri, &block)
           cached_file, downloaded = from_immutable_caches(uri), false unless cached_file
 
           fail "Unable to find cached file for #{uri}" unless cached_file
-          cached_file.cached(File::RDONLY, downloaded, &block)
+          cached_file.cached(File::RDONLY | File::BINARY, downloaded, &block)
         end
 
         # Removes an item from the mutable cache.
@@ -135,7 +135,7 @@ def attempt(http, request, cached_file)
         end
 
         def cache_content(response, cached_file)
-          cached_file.cached(File::CREAT | File::WRONLY) do |f|
+          cached_file.cached(File::CREAT | File::WRONLY | File::BINARY) do |f|
             @logger.debug { "Persisting content to #{f.path}" }
 
             f.truncate(0)
@@ -153,7 +153,7 @@ def cache_etag(response, cached_file)
 
           @logger.debug { "Persisting etag: #{etag}" }
 
-          cached_file.etag(File::CREAT | File::WRONLY) do |f|
+          cached_file.etag(File::CREAT | File::WRONLY | File::BINARY) do |f|
             f.truncate(0)
             f.write etag
             f.fsync
@@ -167,7 +167,7 @@ def cache_last_modified(response, cached_file)
 
           @logger.debug { "Persisting last-modified: #{last_modified}" }
 
-          cached_file.last_modified(File::CREAT | File::WRONLY) do |f|
+          cached_file.last_modified(File::CREAT | File::WRONLY | File::BINARY) do |f|
             f.truncate(0)
             f.write last_modified
             f.fsync
@@ -223,11 +223,11 @@ def request(uri, cached_file)
           request = Net::HTTP::Get.new(uri.request_uri)
 
           if cached_file.etag?
-            cached_file.etag(File::RDONLY) { |f| request['If-None-Match'] = File.read(f) }
+            cached_file.etag(File::RDONLY | File::BINARY) { |f| request['If-None-Match'] = File.read(f) }
           end
 
           if cached_file.last_modified?
-            cached_file.last_modified(File::RDONLY) { |f| request['If-Modified-Since'] = File.read(f) }
+            cached_file.last_modified(File::RDONLY | File::BINARY) { |f| request['If-Modified-Since'] = File.read(f) }
           end
 
           @logger.debug { "Request: #{request.path}, #{request.to_hash}" }

spec/java_buildpack/util/cache/cached_file_spec.rb

@@ -80,7 +80,7 @@
   end
 
   def cache_file(extension)
-    app_dir + "http:%2F%2Ffoo-uri%2F.#{extension}"
+    app_dir + "http%3A%2F%2Ffoo-uri%2F.#{extension}"
   end
 
   def touch(extension, content = '')

spec/java_buildpack/util/cache/download_cache_spec.rb

@@ -241,11 +241,11 @@
   end
 
   def cache_file(root, extension)
-    root + "http:%2F%2Ffoo-uri%2F.#{extension}"
+    root + "http%3A%2F%2Ffoo-uri%2F.#{extension}"
   end
 
   def credential_cache_file(root, extension)
-    root + "http:%2F%2Ftest-username:test-password@foo-uri%2F.#{extension}"
+    root + "http%3A%2F%2Ftest-username%3Atest-password@foo-uri%2F.#{extension}"
   end
 
   def expect_complete_cache(root)