--- a/mercurial/revset.py	Fri Oct 26 12:02:58 2012 -0700
+++ b/mercurial/revset.py	Tue Oct 30 18:48:44 2012 -0500
@@ -105,6 +105,15 @@
 keywords = set(['and', 'or', 'not'])
 
 def tokenize(program):
+    '''
+    Parse a revset statement into a stream of tokens
+
+    Check that @ is a valid unquoted token character (issue3686):
+    >>> list(tokenize("@::"))
+    [('symbol', '@', 0), ('::', None, 1), ('end', None, 3)]
+
+    '''
+
     pos, l = 0, len(program)
     while pos < l:
         c = program[pos]
@@ -140,12 +149,12 @@
             else:
                 raise error.ParseError(_("unterminated string"), s)
         # gather up a symbol/keyword
-        elif c.isalnum() or c in '._' or ord(c) > 127:
+        elif c.isalnum() or c in '._@' or ord(c) > 127:
             s = pos
             pos += 1
             while pos < l: # find end of symbol
                 d = program[pos]
-                if not (d.isalnum() or d in "._/" or ord(d) > 127):
+                if not (d.isalnum() or d in "._/@" or ord(d) > 127):
                     break
                 if d == '.' and program[pos - 1] == '.': # special case for ..
                     pos -= 1