shellcheck: fix some warnings

Catch up with shellcheck 0.9.0.

To improve shellcheck usage in chroot-script, add a stub file defining ARCH.

This commit is very minimal. In particular it avoids moving/deduplicating code
and/or any style changes.

chroot-script

@@ -8,6 +8,7 @@
 # GRML_CHROOT_SCRIPT_MARKER - do not remove this line unless you want to keep
 # this script as /bin/chroot-script on your new installed system
 ################################################################################
+# shellcheck disable=SC2317  # shellcheck has trouble understanding the code flow in this file
 
 # error_handler {{{
 if [ "$REPORT_TRAP_ERR" = "yes" ] || [ "$FAIL_TRAP_ERR" = "yes" ]; then
@@ -18,9 +19,9 @@ if [ "$REPORT_TRAP_ERR" = "yes" ] || [ "$FAIL_TRAP_ERR" = "yes" ]; then
 fi
 # }}}
 
-# shellcheck disable=SC1091
+# shellcheck source=config
 . /etc/debootstrap/config    || exit 1
-# shellcheck disable=SC1091
+# shellcheck source=tests/shellcheck-stub-debootstrap-variables
 . /etc/debootstrap/variables || exit 1
 
 [ -r /proc/1 ] || mount -t proc none /proc
@@ -392,6 +393,7 @@ passwords()
   fi
 
   if [ -n "$ROOTPASSWORD" ] ; then
+     # shellcheck disable=SC2086
      echo root:"$ROOTPASSWORD" | chpasswd $CHPASSWD_OPTION
      export ROOTPASSWORD=''
   else
@@ -414,6 +416,7 @@ passwords()
          a='1'
          b='2'
        else
+         # shellcheck disable=SC2086
          echo root:"$a" | chpasswd $CHPASSWD_OPTION
          unset a
          unset b
@@ -601,8 +604,10 @@ initrd() {
      echo "Generating initrd."
      if [ "$INITRD_GENERATOR" = 'dracut' ] ; then
          DEBIAN_FRONTEND=$DEBIAN_FRONTEND $APTINSTALL dracut
+         # shellcheck disable=SC2086
          dracut --no-hostonly --kver "$KERNELVER" --fstab --add-fstab /etc/fstab --force --reproducible $INITRD_GENERATOR_OPTS
      else
+         # shellcheck disable=SC2086
          update-initramfs -c -t -k "$KERNELVER" $INITRD_GENERATOR_OPTS
      fi
   fi
@@ -698,9 +703,9 @@ grub_install() {
   echo "Setting ${GRUB_PACKAGE} debconf configuration for install device to $GRUB"
   echo "${GRUB_PACKAGE} ${GRUB_PACKAGE}/install_devices multiselect ${grub_device}" | debconf-set-selections
 
-  if ! dpkg --list ${GRUB_PACKAGE} 2>/dev/null | grep -q '^ii' ; then
+  if ! dpkg --list "${GRUB_PACKAGE}" 2>/dev/null | grep -q '^ii' ; then
     echo "Notice: grub option set but no ${GRUB_PACKAGE} package, installing it therefore."
-    DEBIAN_FRONTEND=$DEBIAN_FRONTEND $APTINSTALL ${GRUB_PACKAGE}
+    DEBIAN_FRONTEND=$DEBIAN_FRONTEND $APTINSTALL "${GRUB_PACKAGE}"
   fi
 
   if ! [ -x "$(command -v grub-install)" ] ; then

config

@@ -4,6 +4,7 @@
 # Bug-Reports:   see https://grml.org/bugs/
 # License:       This file is licensed under the GPL v2 or any later version.
 ################################################################################
+# shellcheck shell=sh
 
 ################################################################################
 # Important: adjust this file if you want to execute grml-debootstrap

grml-debootstrap

@@ -42,7 +42,7 @@ fi
 # variables {{{
 PN="$(basename "$0")"
 if [[ -d "$(dirname "$(command -v "$0")")"/.git ]]; then
-  VERSION="$(git --git-dir $(dirname "$(command -v "$0")")/.git describe | sed 's|^v||')"
+  VERSION="$(git --git-dir "$(dirname "$(command -v "$0")")"/.git describe | sed 's|^v||')"
 else
   VERSION="$(dpkg-query --show --showformat='${Version}' "$PN")"
 fi
@@ -1950,11 +1950,13 @@ iface ${interface} inet dhcp
     einfo "Installing default /etc/network/interfaces as requested via --defaultinterfaces options."
     mkdir -p "${MNTPOINT}/etc/network"
     echo "$DEFAULT_INTERFACES" > "${MNTPOINT}/etc/network/interfaces"
+    # shellcheck disable=SC2320
     eend $?
   elif [ -n "$VIRTUAL" ] ; then
     einfo "Setting up Virtual Machine, installing default /etc/network/interfaces"
     mkdir -p "${MNTPOINT}/etc/network"
     echo "$DEFAULT_INTERFACES" > "${MNTPOINT}/etc/network/interfaces"
+    # shellcheck disable=SC2320
     eend $?
   elif [ -r /etc/network/interfaces ] ; then
     einfo "Copying /etc/network/interfaces from host to target system"
@@ -1965,6 +1967,7 @@ iface ${interface} inet dhcp
     ewarn "Couldn't read /etc/network/interfaces, installing default /etc/network/interfaces"
     mkdir -p "${MNTPOINT}/etc/network"
     echo "$DEFAULT_INTERFACES" > "${MNTPOINT}/etc/network/interfaces"
+    # shellcheck disable=SC2320
     eend $?
   fi
 

tests/shellcheck-stub-debootstrap-variables

@@ -0,0 +1,7 @@
+# Stub data file for shellcheck runs.
+# shellcheck shell=sh
+# shellcheck disable=SC2034  # The point of our whole existence is to conflict with SC2034.
+
+# ARCH is defaulted in grml-debootstrap, so it is never empty.
+ARCH=amd64
+