fileset: handle underbar in symbols

This was documented, but not implemented.

mercurial/fileset.py

@@ -27,7 +27,7 b' elements = {'
 
 keywords = set(['and', 'or', 'not'])
 
-globchars = ".*{}[]?/\\"
+globchars = ".*{}[]?/\\_"
 
 def tokenize(program):
     pos, l = 0, len(program)

tests/test-fileset.t

@@ -42,6 +42,7 b' Test operators and basic patterns'
   b2
   $ fileset 'a* - a1'
   a2
+  $ fileset 'a_b'
 
 Test files status