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

commands/commandeer.go

@@ -521,6 +521,7 @@ func applyLocalFlagsBuildConfig(cmd *cobra.Command, r *rootCommand) {
 	cmd.Flags().StringP("cacheDir", "", "", "filesystem path to cache directory")
 	_ = cmd.Flags().SetAnnotation("cacheDir", cobra.BashCompSubdirsInDir, []string{})
 	cmd.Flags().StringP("contentDir", "c", "", "filesystem path to content directory")
+	cmd.Flags().StringSliceP("renderSegments", "", []string{}, "named segments to render (configured in the segments config)")
 	_ = cmd.Flags().SetAnnotation("theme", cobra.BashCompSubdirsInDir, []string{"themes"})
 }
 

config/allconfig/allconfig.go

@@ -39,6 +39,7 @@ import (
 	"github.com/gohugoio/hugo/config/services"
 	"github.com/gohugoio/hugo/deploy/deployconfig"
 	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/hugolib/segments"
 	"github.com/gohugoio/hugo/langs"
 	"github.com/gohugoio/hugo/markup/markup_config"
 	"github.com/gohugoio/hugo/media"
@@ -139,6 +140,9 @@ type Config struct {
 	// a slice of page matcher and params to apply to those pages.
 	Cascade *config.ConfigNamespace[[]page.PageMatcherParamsConfig, map[page.PageMatcher]maps.Params] `mapstructure:"-"`
 
+	// The segments defines segments for the site. Used for partial/segmented builds.
+	Segments *config.ConfigNamespace[map[string]segments.SegmentConfig, segments.Segments] `mapstructure:"-"`
+
 	// Menu configuration.
 	// <docsmeta>{"refs": ["config:languages:menus"] }</docsmeta>
 	Menus *config.ConfigNamespace[map[string]navigation.MenuConfig, navigation.Menus] `mapstructure:"-"`
@@ -366,6 +370,7 @@ func (c *Config) CompileConfig(logger loggers.Logger) error {
 		CreateTitle:       helpers.GetTitleFunc(c.TitleCaseStyle),
 		IsUglyURLSection:  isUglyURL,
 		IgnoreFile:        ignoreFile,
+		SegmentFilter:     c.Segments.Config.Get(func(s string) { logger.Warnf("Render segment %q not found in configuration", s) }, c.RootConfig.RenderSegments...),
 		MainSections:      c.MainSections,
 		Clock:             clock,
 		transientErr:      transientErr,
@@ -402,6 +407,7 @@ type ConfigCompiled struct {
 	CreateTitle       func(s string) string
 	IsUglyURLSection  func(section string) bool
 	IgnoreFile        func(filename string) bool
+	SegmentFilter     segments.SegmentFilter
 	MainSections      []string
 	Clock             time.Time
 
@@ -474,6 +480,10 @@ type RootConfig struct {
 	// A list of languages to disable.
 	DisableLanguages []string
 
+	// The named segments to render.
+	// This needs to match the name of the segment in the segments configuration.
+	RenderSegments []string
+
 	// Disable the injection of the Hugo generator tag on the home page.
 	DisableHugoGeneratorInject bool
 

config/allconfig/alldecoders.go

@@ -25,11 +25,13 @@ import (
 	"github.com/gohugoio/hugo/config/security"
 	"github.com/gohugoio/hugo/config/services"
 	"github.com/gohugoio/hugo/deploy/deployconfig"
+	"github.com/gohugoio/hugo/hugolib/segments"
 	"github.com/gohugoio/hugo/langs"
 	"github.com/gohugoio/hugo/markup/markup_config"
 	"github.com/gohugoio/hugo/media"
 	"github.com/gohugoio/hugo/minifiers"
 	"github.com/gohugoio/hugo/modules"
+
 	"github.com/gohugoio/hugo/navigation"
 	"github.com/gohugoio/hugo/output"
 	"github.com/gohugoio/hugo/related"
@@ -120,6 +122,14 @@ var allDecoderSetups = map[string]decodeWeight{
 			return err
 		},
 	},
+	"segments": {
+		key: "segments",
+		decode: func(d decodeWeight, p decodeConfig) error {
+			var err error
+			p.c.Segments, err = segments.DecodeSegments(p.p.GetStringMap(d.key))
+			return err
+		},
+	},
 	"server": {
 		key: "server",
 		decode: func(d decodeWeight, p decodeConfig) error {

hugolib/hugo_sites.go

@@ -410,6 +410,10 @@ type BuildCfg struct {
 
 // shouldRender returns whether this output format should be rendered or not.
 func (cfg *BuildCfg) shouldRender(p *pageState) bool {
+	if p.skipRender() {
+		return false
+	}
+
 	if !p.renderOnce {
 		return true
 	}

hugolib/hugo_sites_build.go

@@ -28,16 +28,16 @@ import (
 	"github.com/bep/logg"
 	"github.com/gohugoio/hugo/cache/dynacache"
 	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/hugofs"
 	"github.com/gohugoio/hugo/hugofs/files"
 	"github.com/gohugoio/hugo/hugofs/glob"
+	"github.com/gohugoio/hugo/hugolib/segments"
 	"github.com/gohugoio/hugo/identity"
 	"github.com/gohugoio/hugo/output"
 	"github.com/gohugoio/hugo/publisher"
 	"github.com/gohugoio/hugo/source"
 	"github.com/gohugoio/hugo/tpl"
 
-	"github.com/gohugoio/hugo/hugofs"
-
 	"github.com/gohugoio/hugo/common/herrors"
 	"github.com/gohugoio/hugo/common/loggers"
 	"github.com/gohugoio/hugo/common/para"
@@ -318,9 +318,20 @@ func (h *HugoSites) render(l logg.LevelLogger, config *BuildCfg) error {
 
 	i := 0
 	for _, s := range h.Sites {
+		segmentFilter := s.conf.C.SegmentFilter
+		if segmentFilter.ShouldExcludeCoarse(segments.SegmentMatcherFields{Lang: s.language.Lang}) {
+			l.Logf("skip language %q not matching segments set in --renderSegments", s.language.Lang)
+			continue
+		}
+
 		siteRenderContext.languageIdx = s.languagei
 		h.currentSite = s
 		for siteOutIdx, renderFormat := range s.renderFormats {
+			if segmentFilter.ShouldExcludeCoarse(segments.SegmentMatcherFields{Output: renderFormat.Name, Lang: s.language.Lang}) {
+				l.Logf("skip output format %q for language %q not matching segments set in --renderSegments", renderFormat.Name, s.language.Lang)
+				continue
+			}
+
 			siteRenderContext.outIdx = siteOutIdx
 			siteRenderContext.sitesOutIdx = i
 			i++

hugolib/page.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/gohugoio/hugo/hugofs"
 	"github.com/gohugoio/hugo/hugolib/doctree"
+	"github.com/gohugoio/hugo/hugolib/segments"
 	"github.com/gohugoio/hugo/identity"
 	"github.com/gohugoio/hugo/media"
 	"github.com/gohugoio/hugo/output"
@@ -152,6 +153,19 @@ func (p *pageState) reusePageOutputContent() bool {
 	return p.pageOutputTemplateVariationsState.Load() == 1
 }
 
+func (p *pageState) skipRender() bool {
+	b := p.s.conf.C.SegmentFilter.ShouldExcludeFine(
+		segments.SegmentMatcherFields{
+			Path:   p.Path(),
+			Kind:   p.Kind(),
+			Lang:   p.Lang(),
+			Output: p.pageOutput.f.Name,
+		},
+	)
+
+	return b
+}
+
 func (po *pageState) isRenderedAny() bool {
 	for _, o := range po.pageOutputs {
 		if o.isRendered() {