Allow PostReceivePack to be enabled with Gitaly

lib/gitlab/workhorse.rb

@@ -31,8 +31,7 @@ module Gitlab
           feature_enabled = case action.to_s
                             when 'git_receive_pack'
-                              # Disabled for now, see https://gitlab.com/gitlab-org/gitaly/issues/172
-                              false
+                              Gitlab::GitalyClient.feature_enabled?(:post_receive_pack)
                             when 'git_upload_pack'
                               Gitlab::GitalyClient.feature_enabled?(:post_upload_pack)
                             when 'info_refs'

spec/lib/gitlab/workhorse_spec.rb

@@ -244,7 +244,7 @@ describe Gitlab::Workhorse, lib: true do
       context "when git_receive_pack action is passed" do
         let(:action) { 'git_receive_pack' }
-        it { expect(subject).not_to include(gitaly_params) }
+        it { expect(subject).to include(gitaly_params) }
       end
       context "when info_refs action is passed" do