mv: prevent mismatched data when ignoring errors.

We shrink the source and destination arrays, but not the modes or
submodule_gitfile arrays, resulting in potentially mismatched data.  Shrink
all the arrays at the same time to prevent this.  Add tests to ensure the
problem does not recur.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>