Use base SHA for patches and diffs

This commit changes the revisions used for diffs. The current behaviour is
to show all changes between current tip of master and tip of the MR, rather
than matching the output of the web frontend (which just shows the changes
in the MR). Switching from start_sha to base_sha fixes this.

lib/gitlab/workhorse.rb

@@ -60,7 +60,7 @@ module Gitlab
       def send_git_diff(repository, diff_refs)
         params = {
           'RepoPath'  => repository.path_to_repo,
-          'ShaFrom'   => diff_refs.start_sha,
+          'ShaFrom'   => diff_refs.base_sha,
           'ShaTo'     => diff_refs.head_sha
         }
 
@@ -73,7 +73,7 @@ module Gitlab
       def send_git_patch(repository, diff_refs)
         params = {
           'RepoPath'  => repository.path_to_repo,
-          'ShaFrom'   => diff_refs.start_sha,
+          'ShaFrom'   => diff_refs.base_sha,
           'ShaTo'     => diff_refs.head_sha
         }
 

spec/lib/gitlab/workhorse_spec.rb

@@ -2,7 +2,15 @@ require 'spec_helper'
 
 describe Gitlab::Workhorse, lib: true do
   let(:project)    { create(:project) }
-  let(:subject) { Gitlab::Workhorse }
+  let(:repository) { project.repository }
+
+  def decode_workhorse_header(array)
+    key, value = array
+    command, encoded_params = value.split(":")
+    params = JSON.parse(Base64.urlsafe_decode64(encoded_params))
+
+    [key, command, params]
+  end
 
   describe ".send_git_archive" do
     context "when the repository doesn't have an archive file path" do
@@ -11,9 +19,35 @@ describe Gitlab::Workhorse, lib: true do
       end
 
       it "raises an error" do
-        expect { subject.send_git_archive(project.repository, ref: "master", format: "zip") }.to raise_error(RuntimeError)
+        expect { described_class.send_git_archive(project.repository, ref: "master", format: "zip") }.to raise_error(RuntimeError)
+      end
     end
   end
+
+  describe '.send_git_patch' do
+    let(:diff_refs) { double(base_sha: "base", head_sha: "head") }
+    subject { described_class.send_git_patch(repository, diff_refs) }
+
+    it 'sets the header correctly' do
+      key, command, params = decode_workhorse_header(subject)
+
+      expect(key).to eq("Gitlab-Workhorse-Send-Data")
+      expect(command).to eq("git-format-patch")
+      expect(params).to eq("RepoPath" => repository.path_to_repo, "ShaFrom" => "base", "ShaTo" => "head")
+    end
+  end
+
+  describe '.send_git_diff' do
+    let(:diff_refs) { double(base_sha: "base", head_sha: "head") }
+    subject { described_class.send_git_patch(repository, diff_refs) }
+
+    it 'sets the header correctly' do
+      key, command, params = decode_workhorse_header(subject)
+
+      expect(key).to eq("Gitlab-Workhorse-Send-Data")
+      expect(command).to eq("git-format-patch")
+      expect(params).to eq("RepoPath" => repository.path_to_repo, "ShaFrom" => "base", "ShaTo" => "head")
+    end
   end
 
   describe ".secret" do