Improve sections

main.go

@@ -243,6 +243,7 @@ func (h *handler) handlePost(w http.ResponseWriter, r *http.Request, urlPath, fs
 	}
 	content := r.FormValue("content")
 	indexPath := filepath.Join(fsPath, "index.md")
+	redirectTarget := urlPath
 
 	// If a section index was submitted, splice the edited section back into
 	// the full file rather than replacing the whole document.
@@ -258,6 +259,15 @@ func (h *handler) handlePost(w http.ResponseWriter, r *http.Request, urlPath, fs
 			sections[sectionIndex] = []byte(content)
 		}
 		content = string(joinSections(sections))
+		// Section index ≥ 1 is a heading-anchored section. Redirect to its
+		// anchor so the user lands on the section they just saved, even if
+		// the heading text changed.
+		if sectionIndex >= 1 {
+			ids := headingIDs([]byte(content))
+			if sectionIndex-1 < len(ids) {
+				redirectTarget = urlPath + "#" + ids[sectionIndex-1]
+			}
+		}
 	}
 
 	if strings.TrimSpace(content) == "" {
@@ -275,7 +285,7 @@ func (h *handler) handlePost(w http.ResponseWriter, r *http.Request, urlPath, fs
 			return
 		}
 	}
-	http.Redirect(w, r, urlPath, http.StatusSeeOther)
+	http.Redirect(w, r, redirectTarget, http.StatusSeeOther)
 }
 
 // readPageSettings parses a .page-settings file in dir.