Update README cache key to use full project namespace

app/helpers/projects_helper.rb

@@ -296,7 +296,7 @@ module ProjectsHelper
 
   def readme_cache_key
     sha = @project.commit.try(:sha) || 'nil'
-    [@project.id, sha, "readme"].join('-')
+    [@project.path_with_namespace, sha, "readme"].join('-')
   end
 
   def round_commit_count(project)

spec/helpers/projects_helper_spec.rb

@@ -61,13 +61,13 @@ describe ProjectsHelper do
     end
 
     it "returns a valid cach key" do
-      expect(helper.send(:readme_cache_key)).to eq("#{project.id}-#{project.commit.id}-readme")
+      expect(helper.send(:readme_cache_key)).to eq("#{project.path_with_namespace}-#{project.commit.id}-readme")
     end
 
     it "returns a valid cache key if HEAD does not exist" do
       allow(project).to receive(:commit) { nil }
 
-      expect(helper.send(:readme_cache_key)).to eq("#{project.id}-nil-readme")
+      expect(helper.send(:readme_cache_key)).to eq("#{project.path_with_namespace}-nil-readme")
     end
   end
 end