convert: fix builtin cvsps under Windows
Drafted and reviewed by Frank Kingswood <frank@kingswood-consulting.co.uk>.
dirstate._dirs: fix refcounting broken by
7dfac37cfabf
reported by Patrick Waugh
diff: pass contexts to status
Allow status() to take contexts as well as nodes. This lets us avoid
unpacking manifests multiple times and intelligently unpack manifests
in revision order. Also, we can avoid unpacking manifests at all when
there are no changes in the working directory.