dotfiles/.config/nixpkgs/elvish/lib/nix-shell.elv

use path

# nix-shell overwrites TMPDIR so set it back to the original value
if (and (has-env ORIG_TMPDIR) (has-env IN_NIX_SHELL)) {
  set-env TMPDIR $E:ORIG_TMPDIR
} elif (has-env TMPDIR) {
  set-env ORIG_TMPDIR $E:TMPDIR
}

edit:add-var nix~ {|@a|
  var is-shell = (and ^
    (> (count $a) 0) ^
    (eq $a[0] "develop") ^
    (not (has-value $a "--command" )))

  if $is-shell {
    set a = $a[1..]
    e:nix develop $@a --command elvish
  } else {
    e:nix $@a
  }
}

edit:add-var nix-shell~ {|@a|
  var is-shell = (not (or ^
    (has-value $a "--command") ^
    (has-value $a "--run")))

  if $is-shell {
    e:nix-shell $@a --command elvish
  } else {
    e:nix-shell $@a
  }
}