[Nix-dev] nixos-install source enhancement proposals

[Marc Weber]

What do you think about:
a renaming $mountPoint to $NIXOS_INSTALL_TO because $mountPoint can be
  everything, replacing default /mnt target by $NIXOS_INSTALL_TO as well
  (so that you can install to different directories simultaniously for
  testing if you so desire)
b  changing
        if ! test -e "$NIXOS"; then
            echo "NixOS source directory $NIXOS doesn't exist"
            exit 1
        fi
   to
        [ -e "$NIXOS" ] || fail"NixOS source directory $NIXOS doesn't exist"
   because I feel it's more readable? (This pattern is used 4 times)
   (half the lines of duplication can be thrown away)
c Why mount the root from host on $NIXOS_INSTALL_TO/mnt at all?
  It is mounted to to install the basic system
        chroot $mountPoint @nix@/bin/nix-env \
            -p /nix/var/nix/profiles/system \
            -f "/mnt$NIXOS/system/system.nix" \
            --arg configuration "import $NIXOS_CONFIG" \
            --set -A system
  After that the $NIXOS_INSTALL_TO/etc/nixos/ source code is backed up
  and replaced by $NIXOS(_SRC). So the installation step could be done
  at this point and mounting the root from host is no longer necessary

e Do we really want to have this backup stuff?
  It has bitten me because I've edited the code and there was no change
  (because it was backed up..)
  I'd like to replace it by some kind of generic "get-nixos-source"
  function similar to how build phases can be defined (?)
  So ideally you could do something like
  NIXOS_SRC=take_from_host (which means cd / dvd when installing from cd / dvd )
  NIXOS_SRC=svn # default nix svn repo everyone is using (maybe copy
        over from host and only do some update?)
  NIXOS_SRC=git; NIXOS_SRC_GIT_URI=git://myserver/path/ # so that you could use your own modifications
  path should contain nixpks, nixos, system etc

f document NIXOS(_SRC) at the top of file

g make NIXOS_INSTALL_GRUB optional and document it at the top as well ?