Handle v2 manifest diffs

- Accomplish this by merging the "web" process into the top level hash
on the left side of the diff. If the user passed manifest (the right
side of the diff) specifies these keys, then a diff may be shown. If
they do not, the keys will be omitted from the diff.

[#173802711](https://www.pivotaltracker.com/story/show/173802711)

Co-authored-by: Mona Mohebbi <mmohebbi@pivotal.io>
Co-authored-by: Nick Webb <nwebb@pivotal.io>

Author: monamohebbi

app/actions/space_diff_manifest.rb

@@ -18,6 +18,8 @@ def self.generate_diff(app_manifests, space)
             existing_app.routes,
           )
           existing_app_hash = manifest_presenter.to_hash.deep_stringify_keys['applications'][0]
+          web_process_hash = existing_app_hash['processes'].find { |p| p['type'] == 'web' }
+          existing_app_hash = existing_app_hash.merge(web_process_hash) if web_process_hash
         end
 
         manifest_app_hash.each do |key, value|
@@ -28,7 +30,6 @@ def self.generate_diff(app_manifests, space)
             value,
             include_was: true,
           )
-
           key_diffs.each do |diff|
             diff['path'] = "/applications/#{index}/#{key}" + diff['path']
 

spec/request/space_manifests_spec.rb

@@ -511,6 +511,29 @@
       h.freeze
     end
 
+    context 'when a v2 manifest has a change to the web process' do
+      let(:diff_json) do
+        {
+          diff: a_collection_containing_exactly(
+            { op: 'replace', path: '/applications/0/memory', was: '1024M', value: '256M' },
+          )
+        }
+      end
+
+      let(:yml_manifest) do
+        {
+          'applications' => [
+            {
+              'name' => app1_model.name,
+              'memory' => '256M'
+            }
+          ]
+        }.to_yaml
+      end
+
+      it_behaves_like 'permissions for single object endpoint', ALL_PERMISSIONS
+    end
+
     context 'when there are changes in the manifest' do
       let(:diff_json) do
         {

spec/unit/actions/space_diff_manifest_spec.rb

@@ -114,6 +114,25 @@ module VCAP::CloudController
           ])
         end
       end
+
+      context 'when the user passes in a v2 manifest' do
+        let(:default_manifest) {
+          {
+            'applications' => [
+              {
+                'name' => app1_model.name,
+                'memory' => '256M'
+              }
+            ]
+          }
+        }
+
+        it 'returns the correct diff' do
+          expect(subject).to match_array([
+            { 'op' => 'replace', 'path' => '/applications/0/memory', 'was' => "#{process1.memory}M", 'value' => '256M' },
+          ])
+        end
+      end
     end
   end
 end