--- a/mercurial/help/revsets.txt	Sun Sep 26 13:11:31 2010 -0500
+++ b/mercurial/help/revsets.txt	Fri Sep 24 15:36:53 2010 -0500
@@ -7,8 +7,11 @@
 Identifiers such as branch names must be quoted with single or double
 quotes if they contain characters outside of
 ``[._a-zA-Z0-9\x80-\xff]`` or if they match one of the predefined
-predicates. Special characters can be used in quoted identifiers by
-escaping them, e.g., ``\n`` is interpreted as a newline.
+predicates.
+
+Special characters can be used in quoted identifiers by escaping them,
+e.g., ``\n`` is interpreted as a newline. To prevent them from being
+interpreted, strings can be prefixed with ``r``, e.g. ``r'...'``.
 
 There is a single prefix operator:
 
@@ -82,7 +85,8 @@
   An alias for ``::.`` (ancestors of the working copy's first parent).
 
 ``grep(regex)``
-  Like ``keyword(string)`` but accepts a regex.
+  Like ``keyword(string)`` but accepts a regex. Use ``grep(r'...')``
+  to ensure special escape characters are handled correctly.
 
 ``head()``
   Changeset is a head.

--- a/mercurial/revset.py	Sun Sep 26 13:11:31 2010 -0500
+++ b/mercurial/revset.py	Fri Sep 24 15:36:53 2010 -0500
@@ -48,7 +48,14 @@
             pos += 1 # skip ahead
         elif c in "():,-|&+!": # handle simple operators
             yield (c, None, pos)
-        elif c in '"\'': # handle quoted strings
+        elif (c in '"\'' or c == 'r' and
+              program[pos:pos + 2] in ("r'", 'r"')): # handle quoted strings
+            if c == 'r':
+                pos += 1
+                c = program[pos]
+                decode = lambda x: x
+            else:
+                decode = lambda x: x.decode('string-escape')
             pos += 1
             s = pos
             while pos < l: # find closing quote
@@ -57,7 +64,7 @@
                     pos += 2
                     continue
                 if d == c:
-                    yield ('string', program[s:pos].decode('string-escape'), s)
+                    yield ('string', decode(program[s:pos]), s)
                     break
                 pos += 1
             else:

--- a/tests/test-revset.t	Sun Sep 26 13:11:31 2010 -0500
+++ b/tests/test-revset.t	Fri Sep 24 15:36:53 2010 -0500
@@ -215,6 +215,14 @@
   ('func', ('symbol', 'grep'), ('string', '('))
   hg: parse error: invalid match pattern: unbalanced parenthesis
   [255]
+  $ try 'grep("\bissue\d+")'
+  ('func', ('symbol', 'grep'), ('string', '\x08issue\\d+'))
+  $ try 'grep(r"\bissue\d+")'
+  ('func', ('symbol', 'grep'), ('string', '\\bissue\\d+'))
+  6
+  $ try 'grep(r"\")'
+  hg: parse error at 7: unterminated string
+  [255]
   $ log 'head()'
   0
   1