Add by_sha scope, for use in version finder

This adds a new scope `by_sha` to DesignManagement::Version, and allows
it to be used in the version finder.

ee/app/finders/design_management/versions_finder.rb

@@ -24,6 +24,7 @@ module DesignManagement
 
       items = design_or_collection.versions
       items = by_earlier_or_equal_to(items)
+      items = by_sha(items)
       items.ordered
     end
 
@@ -34,5 +35,11 @@ module DesignManagement
 
       items.earlier_or_equal_to(params[:earlier_or_equal_to])
     end
+
+    def by_sha(items)
+      return items unless params[:sha]
+
+      items.by_sha(params[:sha])
+    end
   end
 end

ee/app/models/design_management/version.rb

@@ -55,6 +55,7 @@ module DesignManagement
     scope :earlier_or_equal_to, -> (version) { where('id <= ?', version) }
     scope :ordered, -> { order(id: :desc) }
     scope :for_issue, -> (issue) { where(issue: issue) }
+    scope :by_sha, -> (sha) { where(sha: sha) }
 
     # This is the one true way to create a Version.
     #

ee/spec/finders/design_management/versions_finder_spec.rb

@@ -79,6 +79,20 @@ describe DesignManagement::VersionsFinder do
             it { is_expected.to contain_exactly(version_1, version_2) }
           end
         end
+
+        describe 'returning versions by SHA' do
+          context 'when argument is the first version' do
+            let(:params) { { sha: version_1.sha } }
+
+            it { is_expected.to contain_exactly(version_1) }
+          end
+
+          context 'when argument is the second version' do
+            let(:params) { { sha: version_2.sha } }
+
+            it { is_expected.to contain_exactly(version_2) }
+          end
+        end
       end
     end
   end

ee/spec/models/design_management/version_spec.rb

@@ -60,6 +60,14 @@ describe DesignManagement::Version do
         end
       end
     end
+
+    describe '.by_sha' do
+      it 'can find versions by sha' do
+        [version_1, version_2].each do |version|
+          expect(described_class.by_sha(version.sha)).to contain_exactly(version)
+        end
+      end
+    end
   end
 
   describe ".create_for_designs" do