fix --include option for files and add test case

coverage.txt

@@ -330,3 +330,5 @@ Needs-QEMU: true
 Test: error-if-stdout-is-tty
 
 Test: variant-custom-timeout
+
+Test: include-deb-file

mmdebstrap

@@ -4282,7 +4282,7 @@ sub main() {
             } elsif ($opt_value =~ /^\.?\.?\//) {
                 # Treat option as a single path name and don't split by comma
                 # or whitespace -- append the normalized path.
-                push @{ $options->{include} }, sanitize_path($opt_value);
+                push @{ $options->{include} }, &{$sanitize_path}($opt_value);
             } else {
                 for my $pkg (split /[,\s]+/, $opt_value) {
                     # strip leading and trailing whitespace
@@ -4294,7 +4294,7 @@ sub main() {
                     # Make paths canonical absolute paths, resolve symlinks
                     # and check if it's an existing file.
                     if ($pkg =~ /^\.?\.?\//) {
-                        $pkg = sanitize_path($pkg);
+                        $pkg = &{$sanitize_path}($pkg);
                     }
                     push @{ $options->{include} }, $pkg;
                 }

tests/include-deb-file

@@ -0,0 +1,21 @@
+#!/bin/sh
+
+set -eu
+export LC_ALL=C.UTF-8
+
+{{ CMD }} --variant=apt \
+	--customize-hook='mkdir "$1"/tmp/apt' \
+	--customize-hook='chroot "$1" env --chdir=/tmp/apt apt-get download busybox' \
+	--customize-hook='copy-out /tmp/apt /tmp' \
+	{{ DIST }} /dev/null {{ MIRROR }}
+pkg="$(find /tmp/apt -type f)"
+# some sanity checks
+[ -f "$pkg" ]
+case $pkg in
+	/tmp/apt/busybox*_{{ HOSTARCH }}.deb) : ;;
+	*) exit 1;;
+esac
+# now try to install that package
+{{ CMD }} --variant=apt --include="$pkg" \
+	--customize-hook='chroot "$1" dpkg-query -W -f="\${Status}\n" busybox | grep "^install ok installed$"' \
+	{{ DIST }} /dev/null {{ MIRROR }}