test-kernel-install: add a simple test that kernel-install copies the files

I opted to tweaking kernel-install to allow overriding config
(with $KERNEL_INSTALL_CONF_ROOT, $KERNEL_INSTALL_PLUGINS). An alternative
would be to build a test environment in test/. We can still do that,
but I think it's nice to have a simple test that is very quick and easy
to debug.

Invocation as installkernel is for #23681.

src/kernel-install/test-kernel-install.sh

@@ -0,0 +1,83 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -eu
+set -o pipefail
+
+kernel_install="${1:?}"
+plugin="${2:?}"
+
+D="$(mktemp --tmpdir --directory "test-kernel-install.XXXXXXXXXX")"
+
+# shellcheck disable=SC2064
+trap "rm -rf '$D'" EXIT INT QUIT PIPE
+mkdir -p "$D/boot"
+mkdir -p "$D/efi"
+mkdir -p "$D/sources"
+
+echo 'buzy image' >"$D/sources/linux"
+echo 'the initrd' >"$D/sources/initrd"
+echo 'the-token' >"$D/sources/entry-token"
+echo 'opt1 opt2' >"$D/sources/cmdline"
+
+cat >"$D/sources/install.conf" <<EOF
+layout=bls
+initrd_generator=none
+# those are overriden by envvars
+BOOT_ROOT="$D/badboot"
+MACHINE_ID=badbadbadbadbadbad6abadbadbadbad
+EOF
+
+export KERNEL_INSTALL_CONF_ROOT="$D/sources"
+export KERNEL_INSTALL_PLUGINS="$plugin"
+export BOOT_ROOT="$D/boot"
+export MACHINE_ID='3e0484f3634a418b8e6a39e8828b03e3'
+
+"$kernel_install" -v add 1.1.1 "$D/sources/linux" "$D/sources/initrd"
+
+entry="$BOOT_ROOT/loader/entries/the-token-1.1.1.conf"
+test -f "$entry"
+grep -qE '^title ' "$entry"
+grep -qE '^version +1.1.1' "$entry"
+grep -qE '^options +opt1 opt2' "$entry"
+grep -qE '^linux .*/the-token/1.1.1/linux' "$entry"
+grep -qE '^initrd .*/the-token/1.1.1/initrd' "$entry"
+
+grep -qE 'image' "$BOOT_ROOT/the-token/1.1.1/linux"
+grep -qE 'initrd' "$BOOT_ROOT/the-token/1.1.1/initrd"
+
+"$kernel_install" inspect
+
+"$kernel_install" -v remove 1.1.1
+test ! -f "$entry"
+test ! -f "$BOOT_ROOT/the-token/1.1.1/linux"
+test ! -f "$BOOT_ROOT/the-token/1.1.1/initrd"
+
+# Invoke kernel-install as installkernel
+ln -s --relative -v "$kernel_install" "$D/sources/installkernel"
+"$D/sources/installkernel" -v 1.1.2 "$D/sources/linux" System.map /somedirignored
+
+entry="$BOOT_ROOT/loader/entries/the-token-1.1.2.conf"
+test -f "$entry"
+grep -qE '^title ' "$entry"
+grep -qE '^version +1.1.2' "$entry"
+grep -qE '^options +opt1 opt2' "$entry"
+grep -qE '^linux .*/the-token/1.1.2/linux' "$entry"
+( ! grep -qE '^initrd' "$entry" )
+
+grep -qE 'image' "$BOOT_ROOT/the-token/1.1.2/linux"
+test ! -e "$BOOT_ROOT/the-token/1.1.2/initrd"
+
+# Check installation with boot counting
+echo '56' >"$D/sources/tries"
+
+"$kernel_install" -v add 1.1.1 "$D/sources/linux" "$D/sources/initrd"
+entry="$BOOT_ROOT/loader/entries/the-token-1.1.1+56.conf"
+test -f "$entry"
+grep -qE '^title ' "$entry"
+grep -qE '^version +1.1.1' "$entry"
+grep -qE '^options +opt1 opt2' "$entry"
+grep -qE '^linux .*/the-token/1.1.1/linux' "$entry"
+grep -qE '^initrd .*/the-token/1.1.1/initrd' "$entry"
+
+grep -qE 'image' "$BOOT_ROOT/the-token/1.1.1/linux"
+grep -qE 'initrd' "$BOOT_ROOT/the-token/1.1.1/initrd"