nix-store --add doesn't update refrences properly

[lolbinarycat]

Steps To Reproduce

$ mkdir /tmp/gcbug
$ ln -s $(realpath /bin/sh) /tmpgcbug/sh
$ nix-store -q --tree $(nix-store --add /tmp/gcbug)
/nix/store/zk2qklkcilxpsxf0xbsi65g0b02ywaj2-gcbug

Expected behavior

the closure of the added path should contain bash.

nix-env --version output
nix-env (Nix) 2.18.1

Additional context

this causes store paths to be garbage collected while still alive. this should not ever happen.

Priorities

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