nix copy --to doesn't copy and attempts a build

[kjeremy]

Describe the bug

I noticed that a download was failing on a remote builder so I tried to copy the missing drv into the remote store via nix copy --to ssh-ng://nix-ssh@10.0.36.99 /nix/store/bl8fbiy8bn7j12dvzq8qiazk36q4xygv-empy-3.3.4.tar.gz.drv.

No copy happens, instead a build is attempted and it fails:

error: builder for '/nix/store/bl8fbiy8bn7j12dvzq8qiazk36q4xygv-empy-3.3.4.tar.gz.drv' failed with exit code 1;
       last 7 log lines:
       >
       > trying http://www.alcyone.com/software/empy/empy-3.3.4.tar.gz
       >   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
       >                                  Dload  Upload   Total   Spent    Left  Speed
       >   0   229    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
       > curl: (22) The requested URL returned error: 404
       > error: cannot download empy-3.3.4.tar.gz from any mirror
       For full logs, run 'nix log /nix/store/bl8fbiy8bn7j12dvzq8qiazk36q4xygv-empy-3.3.4.tar.gz.drv'.

Steps To Reproduce

1. Run nix copy --to some-store something,drv

Expected behavior

I would expect the store path and its dependencies to be copied to the remote store.

nix-env (Nix) 2.11.0

[yorickvP]

Try the --derivation flag

[ajs124]

duplicate of #3696 and #4814