Fix ordering of commits in the network graph.

- We upgraded `rugged` to 0.25.1.1 in !10286 for %9.1

- Prior to this upgrade, the default sort order for commits returned by
  `Gitlab::Git::Repository#find_commits` was `Rugged::SORT_DATE`, which the
  graph relied on.

- While upgrading `rugged`, the MR also changed this default to
  `Rugged::SORT_NONE`, which broke commit ordering in the graph.

- This commit adds an option to `Gitlab::Git::Repository#find_commits` to sort
  by date, and changes the graph builder `Network::Graph` so it explictly
  requests the `:date` sort order

2 files changed, 50 insertions, 0 deletions

diff --git a/spec/lib/gitlab/git/repository_spec.rb b/spec/lib/gitlab/git/repository_spec.rb
index 3d6d7292b42..f88653cb1fe 100644
--- a/spec/lib/gitlab/git/repository_spec.rb
+++ b/spec/lib/gitlab/git/repository_spec.rb
@@ -1031,6 +1031,35 @@ describe Gitlab::Git::Repository, seed_helper: true do
     end
   end
 
+  describe '#find_commits' do
+    it 'should return a return a collection of commits' do
+      commits = repository.find_commits
+
+      expect(commits).not_to be_empty
+      expect(commits).to all( be_a_kind_of(Gitlab::Git::Commit) )
+    end
+
+    context 'while applying a sort order based on the `order` option' do
+      it "allows ordering topologically (no parents shown before their children)" do
+        expect_any_instance_of(Rugged::Walker).to receive(:sorting).with(Rugged::SORT_TOPO)
+
+        repository.find_commits(order: :topo)
+      end
+
+      it "allows ordering by date" do
+        expect_any_instance_of(Rugged::Walker).to receive(:sorting).with(Rugged::SORT_DATE)
+
+        repository.find_commits(order: :date)
+      end
+
+      it "applies no sorting by default" do
+        expect_any_instance_of(Rugged::Walker).to receive(:sorting).with(Rugged::SORT_NONE)
+
+        repository.find_commits
+      end
+    end
+  end
+
   describe '#branches with deleted branch' do
     before(:each) do
       ref = double()
diff --git a/spec/models/network/graph_spec.rb b/spec/models/network/graph_spec.rb
index 492c4e01bd8..46b36e11c23 100644
--- a/spec/models/network/graph_spec.rb
+++ b/spec/models/network/graph_spec.rb
@@ -9,4 +9,25 @@ describe Network::Graph, models: true do
 
     expect(graph.notes).to eq( { note_on_commit.commit_id => 1 } )
   end
+
+  describe "#commits" do
+    let(:graph) { described_class.new(project, 'refs/heads/master', project.repository.commit, nil) }
+
+    it "returns a list of commits" do
+      commits = graph.commits
+
+      expect(commits).not_to be_empty
+      expect(commits).to all( be_kind_of(Network::Commit) )
+    end
+
+    it "sorts the commits by commit date (descending)" do
+      # Remove duplicate timestamps because they make it harder to
+      # assert that the commits are sorted as expected.
+      commits = graph.commits.uniq(&:date)
+      sorted_commits = commits.sort_by(&:date).reverse
+
+      expect(commits).not_to be_empty
+      expect(commits.map(&:id)).to eq(sorted_commits.map(&:id))
+    end
+  end
 end