Add Hugo Modules

This commit implements Hugo Modules.

This is a broad subject, but some keywords include:

* A new `module` configuration section where you can import almost anything. You can configure both your own file mounts nd the file mounts of the modules you import. This is the new recommended way of configuring what you earlier put in `configDir`, `staticDir` etc. And it also allows you to mount folders in non-Hugo-projects, e.g. the `SCSS` folder in the Bootstrap GitHub project.
* A module consists of a set of mounts to the standard 7 component types in Hugo: `static`, `content`, `layouts`, `data`, `assets`, `i18n`, and `archetypes`. Yes, Theme Components can now include content, which should be very useful, especially in bigger multilingual projects.
* Modules not in your local file cache will be downloaded automatically and even "hot replaced" while the server is running.
* Hugo Modules supports and encourages semver versioned modules, and uses the minimal version selection algorithm to resolve versions.
* A new set of CLI commands are provided to manage all of this: `hugo mod init`,  `hugo mod get`,  `hugo mod graph`,  `hugo mod tidy`, and  `hugo mod vendor`.

All of the above is backed by Go Modules.

Fixes #5973
Fixes #5996
Fixes #6010
Fixes #5911
Fixes #5940
Fixes #6074
Fixes #6082
Fixes #6092

hugolib/taxonomy_test.go

@@ -64,14 +64,15 @@ YAML frontmatter with tags and categories taxonomy.`
 //
 func TestTaxonomiesWithAndWithoutContentFile(t *testing.T) {
 	for _, uglyURLs := range []bool{false, true} {
+		uglyURLs := uglyURLs
 		t.Run(fmt.Sprintf("uglyURLs=%t", uglyURLs), func(t *testing.T) {
+			t.Parallel()
 			doTestTaxonomiesWithAndWithoutContentFile(t, uglyURLs)
 		})
 	}
 }
 
 func doTestTaxonomiesWithAndWithoutContentFile(t *testing.T, uglyURLs bool) {
-	t.Parallel()
 
 	siteConfig := `
 baseURL = "http://example.com/blog"
@@ -104,25 +105,20 @@ permalinkeds:
 
 	siteConfig = fmt.Sprintf(siteConfig, uglyURLs)
 
-	th, h := newTestSitesFromConfigWithDefaultTemplates(t, siteConfig)
-	require.Len(t, h.Sites, 1)
+	b := newTestSitesBuilder(t).WithConfigFile("toml", siteConfig)
 
-	fs := th.Fs
+	b.WithContent(
+		"p1.md", fmt.Sprintf(pageTemplate, "t1/c1", "- Tag1", "- cAt1", "- o1", "- Pl1"),
+		"p2.md", fmt.Sprintf(pageTemplate, "t2/c1", "- tag2", "- cAt1", "- o1", "- Pl1"),
+		"p3.md", fmt.Sprintf(pageTemplate, "t2/c12", "- tag2", "- cat2", "- o1", "- Pl1"),
+		"p4.md", fmt.Sprintf(pageTemplate, "Hello World", "", "", "- \"Hello Hugo world\"", "- Pl1"),
+		"categories/_index.md", newTestPage("Category Terms", "2017-01-01", 10),
+		"tags/Tag1/_index.md", newTestPage("Tag1 List", "2017-01-01", 10),
+		// https://github.com/gohugoio/hugo/issues/5847
+		"/tags/not-used/_index.md", newTestPage("Unused Tag List", "2018-01-01", 10),
+	)
 
-	writeSource(t, fs, "content/p1.md", fmt.Sprintf(pageTemplate, "t1/c1", "- Tag1", "- cAt1", "- o1", "- Pl1"))
-	writeSource(t, fs, "content/p2.md", fmt.Sprintf(pageTemplate, "t2/c1", "- tag2", "- cAt1", "- o1", "- Pl1"))
-	writeSource(t, fs, "content/p3.md", fmt.Sprintf(pageTemplate, "t2/c12", "- tag2", "- cat2", "- o1", "- Pl1"))
-	writeSource(t, fs, "content/p4.md", fmt.Sprintf(pageTemplate, "Hello World", "", "", "- \"Hello Hugo world\"", "- Pl1"))
-
-	writeNewContentFile(t, fs.Source, "Category Terms", "2017-01-01", "content/categories/_index.md", 10)
-	writeNewContentFile(t, fs.Source, "Tag1 List", "2017-01-01", "content/tags/Tag1/_index.md", 10)
-
-	// https://github.com/gohugoio/hugo/issues/5847
-	writeNewContentFile(t, fs.Source, "Unused Tag List", "2018-01-01", "content/tags/not-used/_index.md", 10)
-
-	err := h.Build(BuildCfg{})
-
-	require.NoError(t, err)
+	b.Build(BuildCfg{})
 
 	// So what we have now is:
 	// 1. categories with terms content page, but no content page for the only c1 category
@@ -138,26 +134,26 @@ permalinkeds:
 	}
 
 	// 1.
-	th.assertFileContent(pathFunc("public/categories/cat1/index.html"), "List", "cAt1")
-	th.assertFileContent(pathFunc("public/categories/index.html"), "Terms List", "Category Terms")
+	b.AssertFileContent(pathFunc("public/categories/cat1/index.html"), "List", "cAt1")
+	b.AssertFileContent(pathFunc("public/categories/index.html"), "Taxonomy Term Page", "Category Terms")
 
 	// 2.
-	th.assertFileContent(pathFunc("public/tags/tag2/index.html"), "List", "tag2")
-	th.assertFileContent(pathFunc("public/tags/tag1/index.html"), "List", "Tag1")
-	th.assertFileContent(pathFunc("public/tags/index.html"), "Terms List", "Tags")
+	b.AssertFileContent(pathFunc("public/tags/tag2/index.html"), "List", "tag2")
+	b.AssertFileContent(pathFunc("public/tags/tag1/index.html"), "List", "Tag1")
+	b.AssertFileContent(pathFunc("public/tags/index.html"), "Taxonomy Term Page", "Tags")
 
 	// 3.
-	th.assertFileContent(pathFunc("public/others/o1/index.html"), "List", "o1")
-	th.assertFileContent(pathFunc("public/others/index.html"), "Terms List", "Others")
+	b.AssertFileContent(pathFunc("public/others/o1/index.html"), "List", "o1")
+	b.AssertFileContent(pathFunc("public/others/index.html"), "Taxonomy Term Page", "Others")
 
 	// 4.
-	th.assertFileContent(pathFunc("public/perma/pl1/index.html"), "List", "Pl1")
+	b.AssertFileContent(pathFunc("public/perma/pl1/index.html"), "List", "Pl1")
 
 	// This looks kind of funky, but the taxonomy terms do not have a permalinks definition,
 	// for good reasons.
-	th.assertFileContent(pathFunc("public/permalinkeds/index.html"), "Terms List", "Permalinkeds")
+	b.AssertFileContent(pathFunc("public/permalinkeds/index.html"), "Taxonomy Term Page", "Permalinkeds")
 
-	s := h.Sites[0]
+	s := b.H.Sites[0]
 
 	// Make sure that each page.KindTaxonomyTerm page has an appropriate number
 	// of page.KindTaxonomy pages in its Pages slice.
@@ -204,7 +200,7 @@ permalinkeds:
 	require.Equal(t, "Hello Hugo world", helloWorld.Title())
 
 	// Issue #2977
-	th.assertFileContent(pathFunc("public/empties/index.html"), "Terms List", "Empties")
+	b.AssertFileContent(pathFunc("public/empties/index.html"), "Taxonomy Term Page", "Empties")
 
 }