clea up and fix a bug

.gitignore

@@ -2,4 +2,4 @@
 /latest-iso-minimal-x86_64-linux
 /latest-iso-graphical-x86_64-linux
 /nixos-in-place-test
-*.iso
+*.iso

install

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/bash
 
 set -eu
 
@@ -28,9 +28,9 @@ log_end "seems sane"
 root_mount=$(mount | grep "/ " | sed 's/ /\n/' | head -n1)
 root_type=$(mount | grep -Eo "/ type \w+" | sed 's/ /\n/g' | tail -n1)
 
-the_only_line() {
-  ERROR_MESSAGE_ZERO=$0
-  ERROR_MESSAGE_MULTIPLE=$1
+expect_one_line() {
+  ERROR_MESSAGE_ZERO=$1
+  ERROR_MESSAGE_MULTIPLE=$2
   (set -eu;
    IFS='' read -r x || (echo "$ERROR_MESSAGE_ZERO" >& 2; exit 1)
    (! IFS='' read -r) || (echo "$ERROR_MESSAGE_MULTIPLE" >& 2; exit 1)
@@ -44,7 +44,7 @@ if [ -d /sys/firmware/efi ]; then
     fdisk -l -o 'Device,Type' |
       grep 'EFI System' |
       sed -r 's_([^ ]*) *EFI System$_\1_' |
-      the_only_line \
+      expect_one_line \
 	"Fdisk found no EFI System Partitions: please specify with -g option" \
 	"Found multiple EFI System Partitions: please specify with -g option")
 else
@@ -56,8 +56,7 @@ else
   elif grep '/dev/vd' <<< "$root_mount"; then
     boot_device=$(echo "$root_mount" | sed "s|[0-9]\+||");
   else
-    echo "Unable to determine your grub boot device! \
-Please specify with the -g option."
+    echo "Unable to determine your grub boot device! Please specify with the -g option."
   fi
 fi
 working_directory=$(mktemp -d)