--- a/mercurial/templater.py	Thu Apr 06 19:24:04 2017 +0200
+++ b/mercurial/templater.py	Sun Apr 09 00:10:54 2017 -0400
@@ -719,7 +719,9 @@
 @templatefunc('latesttag([pattern])')
 def latesttag(context, mapping, args):
     """The global tags matching the given pattern on the
-    most recent globally tagged ancestor of this changeset."""
+    most recent globally tagged ancestor of this changeset.
+    If no such tags exist, the "{tag}" template resolves to
+    the string "null"."""
     if len(args) > 1:
         # i18n: "latesttag" is a keyword
         raise error.ParseError(_("latesttag expects at most one argument"))