atomictempfile: make close() consistent with other file-like objects. The usual contract is that close() makes your writes permanent, so atomictempfile's use of close() to *discard* writes (and rename() to keep them) is rather unexpected. Thus, change it so close() makes things permanent and add a new discard() method to throw them away. discard() is only used internally, in __del__(), to ensure that writes are discarded when an atomictempfile object goes out of scope. I audited mercurial.*, hgext.*, and ~80 third-party extensions, and found no one using the existing semantics of close() to discard writes, so this should be safe.

--- a/mercurial/store.py	Wed Aug 24 05:42:41 2011 -0400
+++ b/mercurial/store.py	Thu Aug 25 20:21:04 2011 -0400
@@ -345,7 +345,7 @@
         fp = self.opener('fncache', mode='wb', atomictemp=True)
         for p in self.entries:
             fp.write(encodedir(p) + '\n')
-        fp.rename()
+        fp.close()
         self._dirty = False
 
     def add(self, fn):