[rubygems/rubygems] Remove MD5 ETag generation from compact index

This was an offramp for generated etags to allow existing caches
to be served until people could upgrade. It has been about 6 months
since the transitional version was released, so we can remove this
transitional code now.

https://github.com/rubygems/rubygems/commit/4ec8cfe611

lib/bundler/compact_index_client/cache_file.rb

@@ -86,11 +86,6 @@ module Bundler
         end
       end
 
-      # remove this method when we stop generating md5 digests for legacy etags
-      def md5
-        @digests && @digests["md5"]
-      end
-
       def digests?
         @digests&.any?
       end

lib/bundler/compact_index_client/updater.rb

@@ -28,7 +28,6 @@ module Bundler
 
         CacheFile.copy(local_path) do |file|
           etag = etag_path.read.tap(&:chomp!) if etag_path.file?
-          etag ||= generate_etag(etag_path, file) # Remove this after 2.5.0 has been out for a while.
 
           # Subtract a byte to ensure the range won't be empty.
           # Avoids 416 (Range Not Satisfiable) responses.
@@ -67,16 +66,6 @@ module Bundler
         etag_path.read.tap(&:chomp!) if etag_path.file?
       end
 
-      # When first releasing this opaque etag feature, we want to generate the old MD5 etag
-      # based on the content of the file. After that it will always use the saved opaque etag.
-      # This transparently saves existing users with good caches from updating a bunch of files.
-      # Remove this behavior after 2.5.0 has been out for a while.
-      def generate_etag(etag_path, file)
-        etag = file.md5.hexdigest
-        CacheFile.write(etag_path, etag)
-        etag
-      end
-
       def etag_from_response(response)
         return unless response["ETag"]
         etag = response["ETag"].delete_prefix("W/")

spec/bundler/bundler/compact_index_client/updater_spec.rb

@@ -119,23 +119,7 @@ RSpec.describe Bundler::CompactIndexClient::Updater do
 
     context "without an etag file" do
       let(:headers) do
-        {
-          "Range" => "bytes=2-",
-          # This MD5 feature should be deleted after sufficient time has passed since release.
-          # From then on, requests that still don't have a saved etag will be made without this header.
-          "If-None-Match" => %("#{Digest::MD5.hexdigest(local_body)}"),
-        }
-      end
-
-      it "saves only the etag_path if generated etag matches" do
-        expect(fetcher).to receive(:call).once.with(remote_path, headers).and_return(response)
-        allow(response).to receive(:is_a?).with(Gem::Net::HTTPPartialContent) { false }
-        allow(response).to receive(:is_a?).with(Gem::Net::HTTPNotModified) { true }
-
-        updater.update(remote_path, local_path, etag_path)
-
-        expect(local_path.read).to eq("abc")
-        expect(%("#{etag_path.read}")).to eq(headers["If-None-Match"])
+        { "Range" => "bytes=2-" }
       end
 
       it "appends the file" do