hugolib: Re-work "fast render" logic in the new flow

Note that this fixes some "live reload" issues recently introduced in non-released code.

Closes #5811
See #5784

hugolib/hugo_sites.go

@@ -569,7 +569,6 @@ func (cfg *BuildCfg) shouldRender(p *pageState) bool {
 		return false
 	}
 	if p.forceRender {
-		p.forceRender = false
 		return true
 	}
 
@@ -577,6 +576,10 @@ func (cfg *BuildCfg) shouldRender(p *pageState) bool {
 		return true
 	}
 
+	if cfg.RecentlyVisited[p.RelPermalink()] {
+		return true
+	}
+
 	if cfg.whatChanged != nil && !p.File().IsZero() {
 		return cfg.whatChanged.files[p.File().Filename()]
 	}

hugolib/hugo_sites_build.go

@@ -288,12 +288,10 @@ func (h *HugoSites) render(config *BuildCfg) error {
 					// needs this set.
 					s2.rc = &siteRenderingContext{Format: renderFormat}
 
-					if !config.PartialReRender {
 					if err := s2.preparePagesForRender(siteRenderContext.sitesOutIdx); err != nil {
 						return err
 					}
 				}
-				}
 
 				if !config.SkipRender {
 					if config.PartialReRender {

hugolib/pagebundler.go

@@ -110,8 +110,9 @@ func (s *siteContentProcessor) process(ctx context.Context) error {
 				panic(fmt.Sprintf("invalid page site: %v vs %v", p.s, s))
 			}
 
-			if s.partialBuild {
+			p.forceRender = s.partialBuild
-				p.forceRender = true
+
+			if p.forceRender {
 				s.site.replacePage(p)
 			} else {
 				s.site.addPage(p)