unpack deletes file if it is a compressed single file with no extension

[oxinabox]

If I have a file called foo which is a gzipped plaintext file (for example), with no extension.
And I unpack it, it will yield another file called foo, overwriting the compressed one.
Which will then be deleted.

Work around is to use
post_fetch_method=x->unpack(x; keep_originals=true)