[PATCH 3 of 3] revset: simplify orderedlazyset creation in spanset method

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at fb.com>
# Date 1410936454 25200
#      Tue Sep 16 23:47:34 2014 -0700
# Node ID d26e9a84e752ca0eaa2533d9a3fd3ab614e17b38
# Parent  862bc6d9cdea929b80bf3635f8b66d7b39ebd6ad
revset: simplify orderedlazyset creation in spanset method

We can simply use the `self.isascending` value instead of more complex if/else
clause. This get the code simpler.

Benchmarks show no performances harmed in the process.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2780,22 +2780,18 @@ class spanset(_orderedsetmixin):
         return False
 
     def __and__(self, x):
         if isinstance(x, baseset):
             x = x.set()
-        if self._start <= self._end:
-            return orderedlazyset(self, x.__contains__)
-        else:
-            return orderedlazyset(self, x.__contains__, ascending=False)
+        return orderedlazyset(self, x.__contains__,
+                              ascending=self.isascending())
 
     def __sub__(self, x):
         if isinstance(x, baseset):
             x = x.set()
-        if self._start <= self._end:
-            return orderedlazyset(self, lambda r: r not in x)
-        else:
-            return orderedlazyset(self, lambda r: r not in x, ascending=False)
+        return orderedlazyset(self, lambda r: r not in x,
+                              ascending=self.isascending())
 
     def __add__(self, x):
         kwargs = {}
         if self.isascending() and x.isascending():
             kwargs['ascending'] = True
@@ -2839,12 +2835,9 @@ class spanset(_orderedsetmixin):
 
     def isdescending(self):
         return self._start >= self._end
 
     def filter(self, l):
-        if self._start <= self._end:
-            return orderedlazyset(self, l)
-        else:
-            return orderedlazyset(self, l, ascending=False)
+        return orderedlazyset(self, l, ascending=self.isascending())
 
 # tell hggettext to extract docstrings from these functions:
 i18nfunctions = symbols.values()