While trying to figure out how `nix-env`/`nix profile` work I had a hard
time understand how man pages were being installed.
Took me quite some time to figure this out, thought it might be useful
to others too!
Fixes#6122, which reports a problem with trying to run the installer
under another user (probably: user is not the disk "owner" and thus
can't mount the volume).
This also makes sure that we get the Docker images from the same Hydra
eval, rather than the latest build from job/nix/.../dockerImage, which
may not be the same.
On Nix 2.6 the output of `nix why-depends --all` seems to be somewhat
off:
$ nix why-depends /nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv /nix/store/srn5jbs1q30jpybdmxqrwskyny659qgc-nix-2.6.drv --derivation --extra-experimental-features nix-command --all
/nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv
└───/nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv
│ └───/nix/store/hm0jmhp8shbf3cl846a685nv4f5cp3fy-nspawn-inst.drv
| [...]
└───/nix/store/2d6q3ygiim9ijl5d4h0qqx6vnjgxywyr-system-units.drv
└───/nix/store/dil014y1b8qyjhhhf5fpaah5fzdf0bzs-unit-systemd-nspawn-hydra.service.drv
└───/nix/store/a9r72wwx8qrxyp7hjydyg0gsrwnn26zb-activate.drv
└───/nix/store/99hlc7i4gl77wq087lbhag4hkf3kvssj-nixos-system-hydra-21.11pre-git.drv
Please note that `[...]-system-units.drv` is supposed to be a direct
child of `[...]-etc.drv`.
The reason for that is that each new level printed by `printNode` is
four spaces off in comparison to `nix why-depends --precise` because the
recursive `printNode()` only prints the path and not the `tree*`-chars in
the case of `--precise` and in this format the path is four spaces further
indented, i.e. on a newline, but on the same level as the path's children, i.e.
/nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv
└───/: …1-p8.drv",["out"]),("/nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv",["out"]),("/nix/store/…
→ /nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv
As you can see `[...]-etc.drv` is a direct child of the root, but four
spaces indented. This logic was directly applied to the code-path with
`precise=false` which resulted in `tree*` being printed four spaces too
deep.
In case of no `--precise`, `hits[hash]` is empty and the path itself
should be printed rather than hits using the same logic as for `hits[hash]`.
With this fix, the output looks correct now:
/nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv
└───/nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv
├───/nix/store/hm0jmhp8shbf3cl846a685nv4f5cp3fy-nspawn-inst.drv
| [...]
└───/nix/store/2d6q3ygiim9ijl5d4h0qqx6vnjgxywyr-system-units.drv
└───/nix/store/dil014y1b8qyjhhhf5fpaah5fzdf0bzs-unit-systemd-nspawn-hydra.service.drv
└───/nix/store/a9r72wwx8qrxyp7hjydyg0gsrwnn26zb-activate.drv
└───/nix/store/99hlc7i4gl77wq087lbhag4hkf3kvssj-nixos-system-hydra-21.11pre-git.drv
