--- a/mercurial/help/revsets.txt	Fri Nov 28 19:50:52 2014 -0500
+++ b/mercurial/help/revsets.txt	Tue Jan 06 23:46:18 2015 +0900
@@ -81,6 +81,19 @@
 defines three aliases, ``h``, ``d``, and ``rs``. ``rs(0:tip, author)`` is
 exactly equivalent to ``reverse(sort(0:tip, author))``.
 
+An infix operator ``##`` can concatenate strings and identifiers into
+one string. For example::
+
+  [revsetalias]
+  issue($1) = grep(r'\bissue[ :]?' ## $1 ## r'\b|\bbug\(' ## $1 ## r'\)')
+
+``issue(1234)`` is equivalent to ``grep(r'\bissue[ :]?1234\b|\bbug\(1234\)')``
+in this case. This matches against all of "issue 1234", "issue:1234",
+"issue1234" and "bug(1234)".
+
+All other prefix, infix and postfix operators have lower priority than
+``##``. For example, ``$1 ## $2~2`` is equivalent to ``($1 ## $2)~2``.
+
 Command line equivalents for :hg:`log`::
 
   -f    ->  ::.