grubby-bls: allow to add many BLS entries for the same kernel image

The BLS files name convention used is ${MACHINE_ID}-${KERNEL_VERSION}.conf
but this means that there can only be a single entry for a given kernel.

Allow the grubby wrapper to add many entries for the same kernel image,
since the old grubby tool was able to do that. To differentiate from the
original BLS entry and to specify that it's a customized entry, add a
[[:digit:]]~custom suffix after the kernel version number.

This will also sort the custom entries before the original entry, that's
also what the old grubby tool did.

Resolves: rhbz#1634752

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

grubby-bls

@@ -260,6 +260,35 @@ remove_bls_fragment() {
     update_grubcfg
 }
 
+get_custom_bls_filename() {
+    local kernelver=$1
+    local bls_target="${blsdir}/${MACHINE_ID}-${kernelver}.conf"
+    count=0
+    local -a files
+    local IFS=$'\n'
+
+    prefix="${bls_target%%.conf}"
+    prefix="${bls_target%%${arch}}"
+    prefix="${prefix%.*}"
+
+    last=($(for bls in ${prefix}.*~custom*.conf ; do
+        if ! [[ -e "${bls}" ]] ; then
+            continue
+        fi
+        bls="${bls##${prefix}.}"
+        bls="${bls%%~custom*}"
+        echo "${bls}"
+    done | tail -n1)) || :
+
+    if [[ -z $last ]]; then
+        last="0"
+    else
+        last=$((last+1))
+    fi
+
+    echo "${bls_target}" | sed -e "s!${prefix}!${prefix}.${last}~custom!"
+}
+
 add_bls_fragment() {
     local kernel="$1" && shift
     local title="$1" && shift
@@ -288,6 +317,12 @@ add_bls_fragment() {
     fi
 
     bls_target="${blsdir}/${MACHINE_ID}-${kernelver}.conf"
+
+    if [[ -e ${bls_target} ]]; then
+        bls_target="$(get_custom_bls_filename "${kernelver}")"
+        print_info "An entry for kernel ${kernelver} already exists, adding ${bls_target}"
+    fi
+
     kernel_dir="/lib/modules/${kernelver}"
     if [[ -f "${kernel_dir}/bls.conf" ]]; then
         cp -aT "${kernel_dir}/bls.conf" "${bls_target}" || exit $?