filterfiles: Search as long as the target is a prefix of current.
filterfiles was failing to find files for directory arguments if
another file existed that started with the directory name and
sorted earlier. For example, a manifest of ('foo.h', 'foo/foo')
would cause filterfiles('foo') to return nothing. This resolves
issue #294.
fix bug in localrepo.changes.
caused by
1e32e2fe8a677c391049d40b8794478976a0a914.
use commit time as mtime for file archives.
now output from two run of "hg archive -t zip" is same.