# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 2014-10-03 08:29:55
# Node ID 36e09c25f8709b0e94ae8c40fd2c7f39811285c5
# Parent  966860f7a1a82ed1181ad63b80521f1fffd8bc1a

baseset: explicitly track order of the baseset

A baseset starts without an explicit order. But as soon as a sort is requested,
we simply register that the baseset has an order and use the ordered version of
the list to behave accordingly.

We will want to properly record the order at creation time in the future. This
would unlock more optimisation and avoid some sorting.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2372,10 +2372,13 @@ class baseset(abstractsmartset):
         return bool(self._list)
 
     def sort(self, reverse=False):
-        self._list.sort(reverse=reverse)
+        self._ascending = not bool(reverse)
 
     def reverse(self):
-        self._list.reverse()
+        if self._ascending is None:
+            self._list.reverse()
+        else:
+            self._ascending = not self._ascending
 
     def __len__(self):
         return len(self._list)
@@ -2421,12 +2424,22 @@ class baseset(abstractsmartset):
 
     def first(self):
         if self:
-            return self._list[0]
+            if self._ascending is None:
+                return self._list[0]
+            elif self._ascending:
+                return self._asclist[0]
+            else:
+                return self._asclist[-1]
         return None
 
     def last(self):
         if self:
-            return self._list[-1]
+            if self._ascending is None:
+                return self._list[-1]
+            elif self._ascending:
+                return self._asclist[-1]
+            else:
+                return self._asclist[0]
         return None
 
 class filteredset(abstractsmartset):