unshelve: add tests for unknown files Adds a basic test for shelving/unshelving with an unknown file present. Adds a test for unshelving on top of an existing unknown file.

unshelve: don't commit unknown files during unshelve (issue4113) Previously, unshelve would temporarily commit unknown files (via addremove) in an attempt to allow unshelving into unknown files. This produced unexpected results, like the file time stamp changing and a .i file being created. This change makes it no longer use addremove. It ignores unknown files completely. If an unshelve would overwrite an unknown file, the unknown file is moved to *.orig The shelve continue/abort format is changed, but it just removes stuff from the end of the file, so it can still read the old format.

largefiles: don't crash on 'local renamed directory' actions a12798938721 introduced splitstandin on all action filenames. It would however crash on 'd' actions where the filename is None. Fix that and add test coverage for that case.