makepkg : check for invalid backup entry

This implements FS#13551

Signed-off-by: Xavier Chantry <shiningxc@gmail.com>
Signed-off-by: Allan McRae <allan@archlinux.org>
Signed-off-by: Dan McGee <dan@archlinux.org>

scripts/makepkg.sh.in

@@ -949,6 +949,18 @@ write_pkginfo() {
 	fi
 }
 
+check_package() {
+	cd "$pkgdir"
+
+	# check existence of backup files
+	local file
+	for file in "${backup[@]}"; do
+		if [ ! -f "$file" ]; then
+			warning "$(gettext "Invalid backup entry : %s")" "$file"
+		fi
+	done
+}
+
 create_package() {
 	if [ ! -d "$pkgdir" ]; then
 		error "$(gettext "Missing pkg/ directory.")"
@@ -956,6 +968,8 @@ create_package() {
 		exit 1 # $E_MISSING_PKGDIR
 	fi
 
+	check_package
+
 	cd "$pkgdir"
 	msg "$(gettext "Creating package...")"
 
@@ -1158,6 +1172,14 @@ check_sanity() {
 		fi
 	done
 
+	local file
+	for file in "${backup[@]}"; do
+		if [ "${file:0:1}" = "/" ]; then
+			error "$(gettext "Invalid backup entry : %s")" "$file"
+			return 1
+		fi
+	done
+
 	if [ "$install" -a ! -f "$install" ]; then
 		error "$(gettext "Install scriptlet (%s) does not exist.")" "$install"
 		return 1