revset: added filter method to revset classes

This method will replace the creation of lazysets inside the revset methods.
Instead, the classes that handle lazy structures will create them based on
their current order.

mercurial/revset.py

@@ -2146,6 +2146,9 b' class baseset(list):'
         l = [r for r in x if r not in s]
         return baseset(list(self) + l)
 
+    def filter(self, l):
+        return lazyset(self, l)
+
 class lazyset(object):
     """Duck type for baseset class which iterates lazily over the revisions in
     the subset and contains a function which tests for membership in the
@@ -2210,6 +2213,9 b' class lazyset(object):'
     def set(self):
         return set([r for r in self])
 
+    def filter(self, l):
+        return lazyset(self, l)
+
 class orderedlazyset(lazyset):
     """Subclass of lazyset which subset can be ordered either ascending or
     descendingly
@@ -2218,6 +2224,9 b' class orderedlazyset(lazyset):'
         super(orderedlazyset, self).__init__(subset, condition)
         self._ascending = ascending
 
+    def filter(self, l):
+        return orderedlazyset(self, l, ascending=self._ascending)
+
 class generatorset(object):
     """Wrapper structure for generators that provides lazy membership and can
     be iterated more than once.
@@ -2357,5 +2366,11 b' class spanset(object):'
     def set(self):
         return self
 
+    def filter(self, l):
+        if self._start <= self._end:
+            return orderedlazyset(self, l)
+        else:
+            return orderedlazyset(self, l, ascending=False)
+
 # tell hggettext to extract docstrings from these functions:
 i18nfunctions = symbols.values()