hugolib: Finish menu vs section content pages

This commit also fixes the default menu sort when the weight is 0.

Closes gohugoio#2974

hugolib/hugo_sites_build.go

@@ -167,6 +167,7 @@ func (h *HugoSites) assemble(config *BuildCfg) error {
 	}
 
 	for _, s := range h.Sites {
+		s.assembleMenus()
 		s.refreshPageCaches()
 		s.setupSitePages()
 	}

hugolib/hugo_sites_build_test.go

@@ -1235,11 +1235,11 @@ lag:
 	return sites
 }
 
-func writeSource(t *testing.T, fs *hugofs.Fs, filename, content string) {
+func writeSource(t testing.TB, fs *hugofs.Fs, filename, content string) {
 	writeToFs(t, fs.Source, filename, content)
 }
 
-func writeToFs(t *testing.T, fs afero.Fs, filename, content string) {
+func writeToFs(t testing.TB, fs afero.Fs, filename, content string) {
 	if err := afero.WriteFile(fs, filepath.FromSlash(filename), []byte(content), 0755); err != nil {
 		t.Fatalf("Failed to write file: %s", err)
 	}

hugolib/menu.go

@@ -157,6 +157,15 @@ var defaultMenuEntrySort = func(m1, m2 *MenuEntry) bool {
 		}
 		return m1.Name < m2.Name
 	}
+
+	if m2.Weight == 0 {
+		return true
+	}
+
+	if m1.Weight == 0 {
+		return false
+	}
+
 	return m1.Weight < m2.Weight
 }