modbuild: better support for build modules in overlays

A new configuration file has been added to map human readable overlay
names to the corresponding directory. The overlay can be specified
with the --overlay option. The passed string can be either a name or a
directory. If a name is passed, this name must map to directory in the
configuration file ${PMODULES_ROOT}/config/overlays.conf. The name is
also used as to select the variant files 'files/variants.name'. The
selection of variant files can be overriden with the --system
option.

Pmodules/libpbuild.bash

@@ -764,12 +764,12 @@ pbuild::make_all() {
 		fi
 
 		modulefile_dir=$(join_by '/' \
-					 "${overlay}/${GROUP}/${PMODULES_MODULEFILES_DIR}" \
+					 "${overlay_dir}/${GROUP}/${PMODULES_MODULEFILES_DIR}" \
 					 "${names[@]}" \
 					 "${module_name}")
 		modulefile_name="${modulefile_dir}/${module_version}"
 		
-		PREFIX="${overlay}/${GROUP}/${module_name}/${module_version}"
+		PREFIX="${overlay_dir}/${GROUP}/${module_name}/${module_version}"
 		local -i i=0
 		for ((i=${#names[@]}-1; i >= 0; i--)); do
 			PREFIX+="/${names[i]}"
@@ -1479,7 +1479,7 @@ pbuild.bootstrap() {
 
 	MODULECMD=$(which true)
 	GROUP='Tools'
-	PREFIX="${overlay}/${GROUP}/Pmodules/${PMODULES_VERSION}"
+	PREFIX="${overlay_dir}/${GROUP}/Pmodules/${PMODULES_VERSION}"
 
 	C_INCLUDE_PATH="${PREFIX}/include"
 	CPLUS_INCLUDE_PATH="${PREFIX}/include"

Pmodules/modbuild.in

@@ -154,7 +154,7 @@ declare         opt_verbose='no'
 # array collecting all modules specified on the command line via '--with=module'
 declare -a      opt_with_modules=()
 
-declare         overlay=''
+declare         opt_overlay_name_or_dir=''
 
 
 parse_args() {
@@ -259,10 +259,10 @@ parse_args() {
 			opt_update_modulefiles='yes'
 			;;
                 --overlay )
-                        overlay=$2
+                        opt_overlay_name_or_dir=$2
                         ;;
                 --overlay=* )
-                        overlay=${1/*=}
+                        opt_overlay_name_or_dir=${1/*=}
                         ;;
                 -- )
                         :
@@ -366,7 +366,6 @@ build_modules() {
                 fi
 	done
 
-        
         local variants=()
         local variants_files=()
         for f in "${files[@]}"; do
@@ -408,15 +407,64 @@ build_modules() {
         done
 }
 
+declare -r OVERLAY_CONF="${PMODULES_ROOT}/${PMODULES_CONFIG_DIR}/overlays.conf"
+
+get_overlay_name_and_dir() {
+	local "$1"
+	local "$2"
+	if [[ -r "${OVERLAY_CONF}" ]]; then
+		local toks=()
+		while read -a toks; do
+			if [[ ${toks[0]} == $3 ]] || [[ ${toks[1]} == $3 ]]; then
+				std::upvar $1  "${toks[0]}"
+				std::upvar $2  "${toks[1]}"
+				return 0
+			fi
+		done < "${OVERLAY_CONF}"
+	fi
+	return 1
+}
+
 #.............................................................................
 # main
 
 parse_args "$@"
 
-if [[ -z "${opt_system}" ]]; then
-        opt_system=$(std::get_os_release)
+#
+# --overlay=name
+#    lookup overlay directory, system name equivalent to overlay name
+# --overlay=name --system=sysname
+#    lookup name, use given system name
+# --overlay=dir
+#    use given overlay dir and default system name
+# --system=name
+#    lookup name, set overlay_dir of found confi
+declare overlay_name=''
+declare overlay_dir=''
+if [[ -n "${opt_overlay_name_or_dir}" ]]; then
+	if ! get_overlay_name_and_dir overlay_name overlay_dir "${opt_overlay_name_or_dir}"; then
+		# not found in config
+		if [[ ${opt_overlay_name_or_dir:0:1} == / ]]; then
+			overlay_dir="${opt_overlay_name_or_dir}"
+		else
+			std::die 1 "Invalid overlay name -- ${opt_overlay_name_or_dir}"
+		fi
+	fi
+	if [[ -z "${opt_system}" ]] && [[ -n "${overlay_name}" ]]; then
+		opt_system="${overlay_name}"
+	fi
+elif [[ -n "${opt_system}" ]]; then
+	get_overlay_name_and_dir overlay_name overlay_dir "${opt_system}" || :
 fi
 
+[[ -z "${overlay_name}" ]] && overlay_name='unknown'
+[[ -z "${overlay_dir}" ]] && overlay_dir="${PMODULES_ROOT}"
+[[ -z "${opt_system}" ]] && opt_system=$(std::get_os_release)
+
+echo overlay_name=$overlay_name
+echo overlay_dir=$overlay_dir
+echo opt_system=$opt_system
+
 pbuild.jobs "${opt_jobs}"
 pbuild.force_rebuild "${opt_force_rebuild}"
 pbuild.build_target "${opt_build_target}"
@@ -441,8 +489,6 @@ fi
 source "${opt_build_config}" || \
         std::die 3 "Oops: Cannot source configuration file -- '$_'"
 
-[[ -z "${overlay}" ]] && overlay=${PMODULES_ROOT}
-
 # :FIXME: should go dist files to
 #         ${PMODULES_ROOT}/var/distfiles
 #         or