Filenames are last in git status --porcelain=2 lines; they
are not escaped in any way, despite the fields being
whitespace-delimited. explode thus happily chops apart filenames
with spaces in them, causing later git operations to operate only on
the filename up to the first space.
Split the lines into the right number of elements -- in all cases,
this is one more than the index we're using, since filenames come last.