Optimize the multilanguage build process

Work In Progress!

This commit makes a rework of the build and rebuild process to better suit a multi-site setup.

This also includes a complete overhaul of the site tests. Previous these were a messy mix that
were testing just small parts of the build chain, some of it testing code-paths not even used in
"real life". Now all tests that depends on a built site follows the same and real production code path.

See #2309
Closes #2211
Closes #477
Closes #1744

hugolib/sitemap_test.go

@@ -37,37 +37,20 @@ const SITEMAP_TEMPLATE = `<urlset xmlns="http://www.sitemaps.org/schemas/sitemap
 </urlset>`
 
 func TestSitemapOutput(t *testing.T) {
-	viper.Reset()
-	defer viper.Reset()
-
-	hugofs.InitMemFs()
+	testCommonResetState()
 
 	viper.Set("baseurl", "http://auth/bub/")
 
 	s := &Site{
-		Source: &source.InMemorySource{ByteSource: weightedSources},
-		Lang:   newDefaultLanguage(),
+		Source:   &source.InMemorySource{ByteSource: weightedSources},
+		Language: newDefaultLanguage(),
 	}
 
-	s.initializeSiteInfo()
-
-	s.prepTemplates("sitemap.xml", SITEMAP_TEMPLATE)
-
-	createPagesAndMeta(t, s)
-
-	if err := s.renderHomePage(); err != nil {
-		t.Fatalf("Unable to RenderHomePage: %s", err)
+	if err := buildAndRenderSite(s, "sitemap.xml", SITEMAP_TEMPLATE); err != nil {
+		t.Fatalf("Failed to build site: %s", err)
 	}
 
-	if err := s.renderSitemap(); err != nil {
-		t.Fatalf("Unable to RenderSitemap: %s", err)
-	}
-
-	if err := s.renderRobotsTXT(); err != nil {
-		t.Fatalf("Unable to RenderRobotsTXT :%s", err)
-	}
-
-	sitemapFile, err := hugofs.Destination().Open("sitemap.xml")
+	sitemapFile, err := hugofs.Destination().Open("public/sitemap.xml")
 
 	if err != nil {
 		t.Fatalf("Unable to locate: sitemap.xml")