Fix branch resource overlapping bundle path

Fixes #13228

hugolib/content_map_page.go

@@ -509,8 +509,23 @@ func (m *pageMap) forEachResourceInPage(
 			// A page key points to the logical path of a page, which when sourced from the filesystem
 			// may represent a directory (bundles) or a single content file (e.g. p1.md).
 			// So, to avoid any overlapping ambiguity, we start looking from the owning directory.
-			ownerKey, _ := m.treePages.LongestPrefixAll(path.Dir(resourceKey))
+			s := resourceKey
-			if ownerKey != keyPage {
+
+			for {
+				s = path.Dir(s)
+				ownerKey, found := m.treePages.LongestPrefixAll(s)
+				if !found {
+					return true, nil
+				}
+				if ownerKey == keyPage {
+					break
+				}
+
+				if s != ownerKey && strings.HasPrefix(s, ownerKey) {
+					// Keep looking
+					continue
+				}
+
 				// Stop walking downwards, someone else owns this resource.
 				rw.SkipPrefix(ownerKey + "/")
 				return false, nil

hugolib/content_map_test.go

@@ -361,6 +361,35 @@ p1-foo.txt
 	b.AssertFileExists("public/s1/p1/index.html", true)
 }
 
+// Issue 13228.
+func TestBranchResourceOverlap(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+-- content/_index.md --
+---
+title: home
+---
+-- content/s1/_index.md --
+---
+title: s1
+---
+-- content/s1x/a.txt --
+a.txt
+-- layouts/index.html --
+Home.
+{{ range .Resources.Match "**" }}
+  {{ .Name }}|
+{{ end }}
+`
+
+	b := Test(t, files)
+
+	b.AssertFileContent("public/index.html", "s1x/a.txt|")
+}
+
 func TestSitemapOverrideFilename(t *testing.T) {
 	t.Parallel()