don't ignore packages added via --include if multiple apt indices are used

coverage.sh

@@ -119,7 +119,7 @@ if [ ! -e shared/hooks/eatmydata/customize.sh ] || [ hooks/eatmydata/customize.s
 	fi
 fi
 starttime=
-total=166
+total=167
 skipped=0
 runtests=0
 i=1
@@ -1858,6 +1858,25 @@ else
 	runtests=$((runtests+1))
 fi
 
+# This checks for https://bugs.debian.org/976166
+# Since $DEFAULT_DIST varies, we hardcode stable and unstable.
+print_header "mode=root,variant=apt: test --include with multiple apt sources"
+cat << END > shared/test.sh
+#!/bin/sh
+set -eu
+export LC_ALL=C.UTF-8
+$CMD --mode=root --variant=minbase --include=doc-debian unstable /tmp/debian-chroot "deb $mirror unstable main" "deb $mirror stable main"
+chroot /tmp/debian-chroot dpkg-query --show doc-debian
+rm -r /tmp/debian-chroot
+END
+if [ "$HAVE_QEMU" = "yes" ]; then
+	./run_qemu.sh
+	runtests=$((runtests+1))
+else
+	./run_null.sh SUDO
+	runtests=$((runtests+1))
+fi
+
 print_header "mode=root,variant=apt: test merged-usr via --setup-hook"
 cat << END > shared/test.sh
 #!/bin/sh

mmdebstrap

@@ -1959,7 +1959,7 @@ sub run_download() {
     ) {
         my %ess_pkgs;
         my %ess_pkgs_target;
-        my %pkgs_to_install_target;
+        my %pkgs_to_install_target = %pkgs_to_install;
         my $num_indices = 0;
         open(
             my $pipe_apt,