Prevent dups when using StringIO for binary reads

lib/gitlab/gitaly_client.rb

@@ -336,6 +336,12 @@ module Gitlab
       s.dup.force_encoding(Encoding::ASCII_8BIT)
     end
 
+    def self.binary_stringio(s)
+      io = StringIO.new(s || '')
+      io.set_encoding(Encoding::ASCII_8BIT)
+      io
+    end
+
     def self.encode_repeated(a)
       Google::Protobuf::RepeatedField.new(:bytes, a.map { |s| self.encode(s) } )
     end

lib/gitlab/gitaly_client/wiki_service.rb

@@ -18,12 +18,11 @@ module Gitlab
           commit_details: gitaly_commit_details(commit_details)
         )
 
-        strio = StringIO.new(content)
+        strio = GitalyClient.binary_stringio(content)
 
         enum = Enumerator.new do |y|
           until strio.eof?
-            chunk = strio.read(MAX_MSG_SIZE)
-            request.content = GitalyClient.encode(chunk)
+            request.content = strio.read(MAX_MSG_SIZE)
 
             y.yield request
 
@@ -46,12 +45,11 @@ module Gitlab
           commit_details: gitaly_commit_details(commit_details)
         )
 
-        strio = StringIO.new(content)
+        strio = GitalyClient.binary_stringio(content)
 
         enum = Enumerator.new do |y|
           until strio.eof?
-            chunk = strio.read(MAX_MSG_SIZE)
-            request.content = GitalyClient.encode(chunk)
+            request.content = strio.read(MAX_MSG_SIZE)
 
             y.yield request