diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
--- a/mercurial/help/config.txt
+++ b/mercurial/help/config.txt
@@ -1629,14 +1629,29 @@ User interface controls.
 ``portablefilenames``
     Check for portable filenames. Can be ``warn``, ``ignore`` or ``abort``.
     (default: ``warn``)
-    If set to ``warn`` (or ``true``), a warning message is printed on POSIX
-    platforms, if a file with a non-portable filename is added (e.g. a file
-    with a name that can't be created on Windows because it contains reserved
-    parts like ``AUX``, reserved characters like ``:``, or would cause a case
-    collision with an existing file).
-    If set to ``ignore`` (or ``false``), no warning is printed.
-    If set to ``abort``, the command is aborted.
-    On Windows, this configuration option is ignored and the command aborted.
+
+    ``warn``
+      Print a warning message on POSIX platforms, if a file with a non-portable
+      filename is added (e.g. a file with a name that can't be created on
+      Windows because it contains reserved parts like ``AUX``, reserved
+      characters like ``:``, or would cause a case collision with an existing
+      file).
+
+    ``ignore``
+      Don't print a warning.
+
+    ``abort``
+      The command is aborted.
+
+    ``true``
+      Alias for ``warn``.
+
+    ``false``
+      Alias for ``ignore``.
+
+    .. container::
+
+      On Windows, this configuration option is ignored and the command aborted.
 
 ``quiet``
     Reduce the amount of output printed. (default: False)