place DPkg::Pre-Install-Pkgs workaround into a new config file

Using APT_CONFIG will render the setting ineffective.

Debian-Bug: #1091442

coverage.txt

@@ -435,3 +435,4 @@ Test: zombie-reaping
 Modes: unshare
 
 Test: empty-suite
+Needs-APT-Config: true

mmdebstrap

@@ -3108,7 +3108,11 @@ sub run_setup() {
     # dpkg-preconfigure should not be needed as we also have set
     # DEBIAN_FRONTEND=noninteractive and DEBCONF_NONINTERACTIVE_SEEN=true and
     # should thus never see debconf prompts. See #1091442 for details.
-    print $conf "#clear DPkg::Pre-Install-Pkgs;\n";
+    {
+        open my $tmp, '>', "$options->{root}/etc/apt/apt.conf.d/99debconf"
+          or error "cannot open /etc/apt/apt.conf.d/99debconf: $!";
+        print $tmp "#clear DPkg::Pre-Install-Pkgs;\n";
+    }
 
     close $conf;
 
@@ -4164,6 +4168,8 @@ sub run_cleanup() {
         # clean up temporary configuration file
         unlink "$options->{root}/etc/apt/apt.conf.d/00mmdebstrap"
           or warning "failed to unlink /etc/apt/apt.conf.d/00mmdebstrap: $!";
+        unlink "$options->{root}/etc/apt/apt.conf.d/99debconf"
+          or warning "failed to unlink /etc/apt/apt.conf.d/99debconf: $!";
 
         if (defined $ENV{APT_CONFIG} && -e $ENV{APT_CONFIG}) {
             unlink $ENV{APT_CONFIG}
@@ -6803,6 +6809,7 @@ sub main() {
     if (any { $_ eq $options->{format} }
         ('tar', 'squashfs', 'ext2', 'ext4', 'null')) {
         if ($options->{format} ne 'null') {
+            #<<< perltidy 20220613 formatting
             if (any { $_ eq $options->{variant} } ('extract', 'custom')
                   and $options->{mode} eq 'fakechroot') {
                 info "creating a tarball, squashfs, ext2 or ext4 image in"
@@ -6810,6 +6817,7 @@ sub main() {
                   . " custom variants because there might be no tar inside the"
                   . " chroot";
             }
+            #>>>
             # try to fail early if target tarball or squashfs image cannot be
             # opened for writing
             if ($options->{target} ne '-') {
@@ -6840,12 +6848,14 @@ sub main() {
         # in unshare and root mode, other users than the current user need to
         # access the rootfs, most prominently, the _apt user. Thus, make the
         # temporary directory world readable.
+        #<<< perltidy 20220613 formatting
         if (
             any { $_ eq $options->{mode} } ('unshare', 'root')
               or ($EFFECTIVE_USER_ID == 0 and $options->{mode} eq 'chrootless')
         ) {
             chmod 0755, $options->{root} or error "cannot chmod root: $!";
         }
+        #>>>
     } elsif ($options->{format} eq 'directory') {
         # user does not seem to have specified a tarball as output, thus work
         # directly in the supplied directory
@@ -7331,9 +7341,11 @@ sub main() {
                     error "cannot copy to standard output: $!";
                 }
             } else {
+                #<<< perltidy 20220613 formatting
                 if (any { $_ eq $options->{format} }
                     ('squashfs', 'ext2', 'ext4')
                       or defined $tar_compressor) {
+                #>>>
                     my @argv = ();
                     if ($options->{format} eq 'squashfs') {
                         push @argv, 'tar2sqfs',

tests/chrootless

@@ -3,6 +3,7 @@ set -eu
 export LC_ALL=C.UTF-8
 export SOURCE_DATE_EPOCH={{ SOURCE_DATE_EPOCH }}
 trap "rm -f /tmp/chrootless.tar /tmp/root.tar" EXIT INT TERM
+before=$(tar --one-file-system --anchored --exclude="./var/log/journal/*" --exclude=./var/log/wtmp -C / -c ./usr ./bin ./etc ./lib ./sbin ./var | md5sum)
 for INCLUDE in '' 'apt' 'apt,build-essential' 'systemd-sysv'; do
   for MODE in root chrootless; do
     {{ CMD }} --mode=$MODE --variant={{ VARIANT }} \
@@ -12,3 +13,8 @@ for INCLUDE in '' 'apt' 'apt,build-essential' 'systemd-sysv'; do
   cmp /tmp/root.tar /tmp/chrootless.tar || diffoscope /tmp/root.tar /tmp/chrootless.tar
   rm /tmp/chrootless.tar /tmp/root.tar
 done
+after=$(tar --one-file-system --anchored --exclude="./var/log/journal/*" --exclude=./var/log/wtmp -C / -c ./usr ./bin ./etc ./lib ./sbin ./var | md5sum)
+if [ "$before" != "$after" ]; then
+  echo "found changes outside the chroot" >&2
+  exit 1
+fi

tests/empty-suite

@@ -3,11 +3,14 @@ set -eu
 export LC_ALL=C.UTF-8
 export SOURCE_DATE_EPOCH={{ SOURCE_DATE_EPOCH }}
 
-trap "rm -f /tmp/debian-chroot.tar" EXIT INT TERM
+trap "rm -f /tmp/debian-chroot1.tar /tmp/debian-chroot2.tar" EXIT INT TERM
 
-{{ CMD }} --variant={{ VARIANT }} --verbose \
+{{ CMD }} --variant={{ VARIANT }} \
+  {{ DIST }} /tmp/debian-chroot1.tar {{ MIRROR }}
+
+{{ CMD }} --variant={{ VARIANT }} \
   --setup-hook='echo deb {{ MIRROR }} {{ DIST }} main >> "$1"/etc/apt/sources.list' \
-  '' /tmp/debian-chroot.tar
+  '' /tmp/debian-chroot2.tar
 
-cmp ./cache/mmdebstrap-{{ DIST }}-{{ VARIANT }}.tar /tmp/debian-chroot.tar \
-  || diffoscope ./cache/mmdebstrap-{{ DIST }}-{{ VARIANT }}.tar /tmp/debian-chroot.tar
+cmp /tmp/debian-chroot1.tar /tmp/debian-chroot2.tar \
+  || diffoscope /tmp/debian-chroot1.tar /tmp/debian-chroot2.tar