make revlog.addgroup pass its file handles to addrevision
This should fix
issue255.
It looks like the problem there happens when addgroup calls addrevision
to add a full revision, and addrevision decides to split the index file
into a .i/.d pair. Since addgroup has an open file handle for the
index file, the renaming of the new .i file to its final name fails on
windows.
Test for
ba7c74081861 (update dirstate correctly for non-branchmerge updates)
(Test case created by Johannes Hofmann)