add more docs that non-empty SUITE will be used to select Essential:yes set

Closes: #1028977

coverage.txt

@@ -358,3 +358,7 @@ Needs-QEMU: true
 Test: jessie-or-older
 Needs-QEMU: true
 Variants: essential apt minbase
+
+Test: apt-patterns
+
+Test: apt-patterns-custom

mmdebstrap

@@ -2374,18 +2374,7 @@ sub run_download() {
             info "nothing to download -- skipping...";
             return ([], \@cached_debs);
         }
-        my @apt_argv = ('install');
-        for my $incl (@{ $options->{include} }) {
-            for my $pkg (split /[,\s]+/, $incl) {
-                # strip leading and trailing whitespace
-                $pkg =~ s/^\s+|\s+$//g;
-                # skip if the remainder is an empty string
-                if ($pkg eq '') {
-                    next;
-                }
-                push @apt_argv, $pkg;
-            }
-        }
+        my @apt_argv = ('install', @{ $options->{include} });
 
         @dl_debs = run_apt_download_progress({
                 APT_ARGV => [@apt_argv],
@@ -2913,20 +2902,9 @@ sub run_essential() {
 sub run_install() {
     my $options = shift;
 
-    my %pkgs_to_install;
-    for my $incl (@{ $options->{include} }) {
-        for my $pkg (split /[,\s]+/, $incl) {
-            # strip leading and trailing whitespace
-            $pkg =~ s/^\s+|\s+$//g;
-            # skip if the remainder is an empty string
-            if ($pkg eq '') {
-                next;
-            }
-            $pkgs_to_install{$pkg} = ();
-        }
-    }
+    my @pkgs_to_install = (@{ $options->{include} });
     if ($options->{variant} eq 'buildd') {
-        $pkgs_to_install{'build-essential'} = ();
+        push @pkgs_to_install, 'build-essential';
     }
     if (any { $_ eq $options->{variant} }
         ('required', 'important', 'standard', 'buildd')) {
@@ -2943,7 +2921,8 @@ sub run_install() {
             $priority = '?and(?or(~prequired,~pimportant,~pstandard),'
               . '?not(?essential))';
         }
-        $pkgs_to_install{
+        push @pkgs_to_install,
+          (
             "?narrow("
               . (
                 length($options->{suite})
@@ -2955,9 +2934,8 @@ sub run_install() {
               )
               . "?architecture($options->{nativearch}),"
               . "$priority)"
-        } = ();
+          );
     }
-    my @pkgs_to_install = keys %pkgs_to_install;
 
     if ($options->{mode} eq 'chrootless') {
         if (scalar @pkgs_to_install > 0) {
@@ -5134,12 +5112,16 @@ sub main() {
                 }
             }
             my $compstr = join " ", @components;
-            # if the currently selected apt keyrings do not contain the
-            # necessary key material for the chosen suite, then attempt adding
-            # a signed-by option
+            # From the suite name we can maybe infer which key we need. If we
+            # can infer this information, then we need to check whether the
+            # currently running apt actually trusts this key or not. If it
+            # doesn't, then we need to add a signed-by line to the sources.list
+            # entry.
             my $signedby        = '';
             my %suite_by_vendor = get_suite_by_vendor();
-            {
+            if (any { $_ eq 'check/signed-by' } @{ $options->{skip} }) {
+                info "skipping check/signed-by as requested";
+            } else {
                 my $keyring
                   = get_keyring_by_suite($options->{suite}, \%suite_by_vendor);
                 if (!defined $keyring) {
@@ -5256,9 +5238,9 @@ sub main() {
                         }
                     }
                     close $fh;
-                }
                     if ($? != 0) {
-                    error "gpg failed";
+                        warning "gpg failed -- cannot infer signed-by value";
+                    }
                 }
             }
             if (scalar @ARGV > 0) {
@@ -6965,6 +6947,8 @@ Upon startup, several checks are carried out, like:
 
 =item * whether the output directory is empty. This check can be disabled using B<--skip=check/empty>
 
+=item * whether adding a C<signed-by> to C<apt/sources.list> is necessary. This requires gpg and can be disabled using B<--skip=check/signed-by>
+
 =back
 
 =item B<setup>
@@ -7004,7 +6988,10 @@ variant uses the fact that libapt treats the C<apt> packages as implicitly
 essential to download only all C<Essential:yes> packages plus apt using
 C<apt-get dist-upgrade>. In the remaining variants, all Packages files
 downloaded by the B<update> step are inspected to find the C<Essential:yes>
-package set as well as all packages of the required priority.
+package set as well as all packages of the required priority. If I<SUITE> is a
+non-empty string, then only packages from the archive with suite or codename
+matching I<SUITE> will be considered for selection of C<Essential:yes>
+packages.
 
 =item B<mount>
 

tests/apt-patterns

@@ -0,0 +1,8 @@
+#!/bin/sh
+set -eu
+export LC_ALL=C.UTF-8
+trap "rm -f /tmp/debian-chroot.tar" EXIT INT TERM
+{{ CMD }} --mode={{ MODE }} --variant=essential \
+	--include '?or(?exact-name(dummy-does-not-exist),?exact-name(apt))' \
+	{{ DIST }} /tmp/debian-chroot.tar {{ MIRROR }}
+tar -tf /tmp/debian-chroot.tar | sort | grep -v ./var/lib/apt/extended_states | diff -u tar1.txt -

tests/apt-patterns-custom

@@ -0,0 +1,9 @@
+#!/bin/sh
+set -eu
+export LC_ALL=C.UTF-8
+trap "rm -f /tmp/debian-chroot.tar" EXIT INT TERM
+{{ CMD }} --mode={{ MODE }} --variant=custom \
+	--include '?narrow(?archive(^{{ DIST }}$),?essential)' \
+	--include apt \
+	{{ DIST }} /tmp/debian-chroot.tar {{ MIRROR }}
+tar -tf /tmp/debian-chroot.tar | sort | diff -u tar1.txt -