Add sysroot.bootloader repo config key

The sysroot.bootloader key configures the bootloader
that OSTree uses when deploying a sysroot. Having this key
allows specifying behavior not to use the default bootloader
backend code, which is preferable when creating a first
deployment from the sysroot (#1774).

As of now, the key can take the values "auto" or "none". If
the key is not given, the value defaults to "auto".

"auto" causes _ostree_sysroot_query_bootloader() to be used
when writing a new deployment, which is the original behavior
that dynamically detects which bootloader to use.

"none" avoids querying the bootloader dynamically. The BLS
config fragments are still written to
sysroot/boot/loader/entries for use by higher-level software.

More values can be supported in future to specify a single
bootloader, different behavior for the bootloader code, or
a list of bootloaders to try.

Resolves: #1774

Closes: #1814
Approved by: jlebon

tests/libtest.sh

@@ -355,6 +355,11 @@ setup_os_boot_grub2() {
     esac
 }
 
+setup_os_boot_configured_bootloader() {
+    bootloader_keyval=$1
+    ${CMD_PREFIX} ostree --repo=sysroot/ostree/repo config set ${bootloader_keyval}
+}
+
 setup_os_repository () {
     mode=$1
     shift
@@ -448,6 +453,9 @@ EOF
         *grub2*)
         setup_os_boot_grub2 "${bootmode}"
             ;;
+        sysroot\.bootloader*)
+        setup_os_boot_configured_bootloader "${bootmode}"
+            ;;
     esac
 
     cd ${test_tmpdir}

tests/test-admin-deploy-none.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+#
+# Copyright (C) 2019 Robert Fairley <rfairley@redhat.com>
+#
+# SPDX-License-Identifier: LGPL-2.0+
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+set -euo pipefail
+
+. $(dirname $0)/libtest.sh
+
+# Exports OSTREE_SYSROOT so --sysroot not needed.
+setup_os_repository "archive" "sysroot.bootloader none"
+
+extra_admin_tests=1
+
+. $(dirname $0)/admin-test.sh
+
+# Test that the bootloader configuration "none" generates BLS config snippets.
+cd ${test_tmpdir}
+rm httpd osdata testos-repo sysroot -rf
+setup_os_repository "archive" "sysroot.bootloader none"
+${CMD_PREFIX} ostree pull-local --repo=sysroot/ostree/repo --remote testos testos-repo testos/buildmaster/x86_64-runtime
+# Test grub2 does not get detected with bootloader configuration "none"
+# (see https://github.com/ostreedev/ostree/issues/1774)
+mkdir -p sysroot/boot/grub2 && touch sysroot/boot/grub2/grub.cfg
+${CMD_PREFIX} ostree admin deploy --karg=root=LABEL=MOO --karg=quiet --os testos testos/buildmaster/x86_64-runtime > out.txt
+assert_file_has_content out.txt "Bootloader updated.*"
+assert_file_has_content sysroot/boot/loader/entries/ostree-1-testos.conf 'options.* root=LABEL=MOO'
+assert_file_has_content sysroot/boot/ostree/testos-${bootcsum}/vmlinuz-3.6.0 'a kernel'
+assert_file_has_content sysroot/boot/ostree/testos-${bootcsum}/initramfs-3.6.0.img 'an initramfs'
+echo "ok generate bls config on first deployment"
+
+# TODO: add tests to try setting with an unsupported bootloader config,
+# once https://github.com/ostreedev/ostree/issues/1827 is solved.
+# The tests should check that the following commands fail:
+#  ${CMD_PREFIX} ostree --repo=sysroot/ostree/repo config set sysroot.bootloader unsupported_bootloader
+#  ${CMD_PREFIX} ostree --repo=sysroot/ostree/repo config set sysroot.bootloader ""