Add segments config + --renderSegments flag

Named segments can be defined in `hugo.toml`.

* Eeach segment consists of zero or more `exclude` filters and zero or more `include` filters.
* Eeach filter consists of one or more field Glob matchers.
* Eeach filter in a section (`exclude` or `include`) is ORed together, each matcher in a filter is ANDed together.

The current list of fields that can be filtered are:

* path as defined in https://gohugo.io/methods/page/path/
* kind
* lang
* output (output format, e.g. html).

It is recommended to put coarse grained filters (e.g. for language and output format) in the excludes section, e.g.:

```toml
[segments.segment1]
  [[segments.segment1.excludes]]
    lang = "n*"
  [[segments.segment1.excludes]]
    no     = "en"
    output = "rss"
  [[segments.segment1.includes]]
    term = "{home,term,taxonomy}"
  [[segments.segment1.includes]]
    path = "{/docs,/docs/**}"
```

By default, Hugo will render all segments, but you can enable filters by setting the `renderSegments` option or `--renderSegments` flag, e.g:

```
hugo --renderSegments segment1,segment2
```

For segment `segment1` in the configuration above, this will:

* Skip rendering of all languages matching `n*`, e.g. `no`.
* Skip rendering of the output format `rss` for the `en` language.
* It will render all pages of kind `home`, `term` or `taxonomy`
* It will render the `/docs` section and all pages below.

Fixes #10106

hugolib/segments/segments_integration_test.go

@@ -0,0 +1,76 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package segments_test
+
+import (
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"github.com/gohugoio/hugo/hugolib"
+)
+
+func TestSegments(t *testing.T) {
+	files := `
+-- hugo.toml --
+baseURL = "https://example.org/"
+renderSegments = ["docs"]
+[languages]
+[languages.en]
+weight = 1
+[languages.no]
+weight = 2
+[languages.nb]
+weight = 3
+[segments]
+[segments.docs]
+[[segments.docs.includes]]
+kind = "{home,taxonomy,term}"
+[[segments.docs.includes]]
+path = "{/docs,/docs/**}"
+[[segments.docs.excludes]]
+path = "/blog/**"
+[[segments.docs.excludes]]
+lang = "n*"
+output = "rss"
+[[segments.docs.excludes]]
+output = "json"
+-- layouts/_default/single.html --
+Single: {{ .Title }}|{{ .RelPermalink }}|
+-- layouts/_default/list.html --
+List: {{ .Title }}|{{ .RelPermalink }}|
+-- content/docs/_index.md --
+-- content/docs/section1/_index.md --
+-- content/docs/section1/page1.md --
+---
+title: "Docs Page 1"
+tags: ["tag1", "tag2"]
+---
+-- content/blog/_index.md --
+-- content/blog/section1/page1.md --
+---
+title: "Blog Page 1"
+tags: ["tag1", "tag2"]
+---
+`
+
+	b := hugolib.Test(t, files)
+	b.Assert(b.H.Configs.Base.RootConfig.RenderSegments, qt.DeepEquals, []string{"docs"})
+
+	b.AssertFileContent("public/docs/section1/page1/index.html", "Docs Page 1")
+	b.AssertFileExists("public/blog/section1/page1/index.html", false)
+	b.AssertFileExists("public/index.html", true)
+	b.AssertFileExists("public/index.xml", true)
+	b.AssertFileExists("public/no/index.html", true)
+	b.AssertFileExists("public/no/index.xml", false)
+}