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/localrepo.py	Wed Aug 24 05:42:41 2011 -0400
+++ b/mercurial/localrepo.py	Thu Aug 25 20:21:04 2011 -0400
@@ -521,7 +521,7 @@
             for label, nodes in branches.iteritems():
                 for node in nodes:
                     f.write("%s %s\n" % (hex(node), encoding.fromlocal(label)))
-            f.rename()
+            f.close()
         except (IOError, OSError):
             pass