File 12888.patch of Package python-Sphinx

diff --git a/sphinx/builders/__init__.py b/sphinx/builders/__init__.py
index 151df6a..c6e5687 100644
--- a/sphinx/builders/__init__.py
+++ b/sphinx/builders/__init__.py
@@ -598,6 +598,9 @@ class Builder:
                     docnames.add(tocdocname)
         docnames.add(self.config.root_doc)
 
+        # sort to ensure deterministic toctree generation
+        self.env.toctree_includes = dict(sorted(self.env.toctree_includes.items()))
+
         with progress_message(__('preparing documents')):
             self.prepare_writing(docnames)
 
diff --git a/sphinx/environment/__init__.py b/sphinx/environment/__init__.py
index 20bfd86..40c2eac 100644
--- a/sphinx/environment/__init__.py
+++ b/sphinx/environment/__init__.py
@@ -752,6 +752,7 @@ class BuildEnvironment:
                     continue
                 logger.warning(__("document isn't included in any toctree"),
                                location=docname)
+        _check_toc_parents(self.toctree_includes)
 
         # call check-consistency for all extensions
         for domain in self.domains.values():
@@ -782,3 +783,24 @@ def _traverse_toctree(
             if sub_docname not in traversed:
                 yield sub_parent, sub_docname
                 traversed.add(sub_docname)
+
+
+def _check_toc_parents(toctree_includes: dict[str, list[str]]) -> None:
+    toc_parents: dict[str, list[str]] = {}
+    for parent, children in toctree_includes.items():
+        for child in children:
+            toc_parents.setdefault(child, []).append(parent)
+
+    for doc, parents in sorted(toc_parents.items()):
+        if len(parents) > 1:
+            logger.info(
+                __(
+                    'document is referenced in multiple toctrees: %s, selecting: %s <- %s'
+                ),
+                parents,
+                max(parents),
+                doc,
+                location=doc,
+                type='toc',
+                subtype='multiple_toc_parents',
+            )