Reorganize configuration root

While I might still bikeshed how the rest of the configuration is
sourced, at least the import points should be stable.

install_os.sh

@@ -0,0 +1,94 @@
+#!/usr/bin/env nix-shell
+#! nix-shell -i bash
+#! nix-shell -p bash nixos-install-tools
+
+set -euo pipefail
+SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+
+# Parse arguments
+function help {
+    echo "Usage: $0 profile [-e]"
+    echo
+    echo "Arguments:"
+    echo "  file: OS/disk profile to use"
+    echo
+    echo "Options:"
+    echo "  -h: Display this help message."
+    echo "  -e: Erase the disk. This can be used in case the wanted partition scheme doesn't match."
+}
+
+disko_mode=mount
+while getopts "e" OPTION
+do
+    case "$OPTION" in
+        h)
+            help
+            exit 0
+            ;;
+        e)
+            disko_mode=disko
+            ;;
+        ?)
+            help
+            exit 2
+            ;;
+    esac
+done
+shift "$(($OPTIND -1))"
+
+if [ "$#" -ne 1 ]
+then
+    help
+    exit 2
+fi
+profile="$1"
+
+profile_dir="${SCRIPT_DIR}/${profile}"
+if [ ! -d "$profile_dir" ]
+then
+    echo "Profile not found."
+fi
+
+disko_config="${profile_dir}/disko.nix"
+if [ ! -f "$disko_config" ]
+then
+    echo "Disk configuration not found."
+fi
+
+nixos_config="${profile_dir}/os.nix"
+if [ ! -f "$nixos_config" ]
+then
+    echo "NixOS configuration not found."
+fi
+
+
+set -x
+
+# Add channels to root user, as nixos-install uses those.
+# Not great, but fixable with flakes I guess
+sudo ./add_channels.sh
+
+# Format or mount disk
+sudo nix --extra-experimental-features nix-command --extra-experimental-features flakes run github:nix-community/disko -- --mode "$disko_mode" "$disko_config"
+
+# Generate hardware-config.nix
+sudo nixos-generate-config --no-filesystems --root /mnt
+# --no-filesystems because they are imported via disko
+
+# Plug system configuration into this git repo
+sudo mkdir -p /mnt/etc/nixos
+echo "{ ... }: { imports = [ ./hardware-configuration.nix ${nixos_config} ]; }" | sudo tee /mnt/etc/nixos/configuration.nix > /dev/null
+# Everything there should be covered by (and conflicts with) the repo anyways.
+
+# Install NixOS! Or create a new generation.
+sudo nixos-install --no-root-password
+
+# Install dotfiles. Actually not needed by nixos-install since it doesn't rewrite global paths to /mnt.
+# Without it no nixos-rebuild from the system itself once installed though.
+# Should probably be replaced with something like git-sync
+# sudo mkdir -p /mnt/home/geoffrey/.config/
+# sudo cp -a ../dotfiles /mnt/home/geoffrey/.config/
+# sudo chown geoffrey:geoffrey /mnt/home/geoffrey -R
+
+# Signal the installation is done!
+echo