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/revlog.py	Wed Aug 24 05:42:41 2011 -0400
+++ b/mercurial/revlog.py	Thu Aug 25 20:21:04 2011 -0400
@@ -946,9 +946,9 @@
             e = self._io.packentry(self.index[i], self.node, self.version, i)
             fp.write(e)
 
-        # if we don't call rename, the temp file will never replace the
+        # if we don't call close, the temp file will never replace the
         # real index
-        fp.rename()
+        fp.close()
 
         tr.replace(self.indexfile, trindex * self._io.size)
         self._chunkclear()