fix recompute of renamed files

fix recompute of renamed files

When a computed file has been renamed, a recompute needs to write to the
new filename.

I decided to remove --others because it's not clear what it should do in
the face of renames. Should it update only other files that have not
been renamed? Or update files that use the old key to the new key
anywhere in the tree? Or write the other files to the cwd, ignoring
renames? Since --others is just a way to save on compute time, adding
this complexity at this point seems like a bad idea. May revisit later.

Added temporary TODO-compute file