src/winusb: Support distros which uses grub2 as prefix name, fixes #94

Refer: use grub2-install when possible by aaptel · Pull Request #99 · slacka/WinUSB <#99>
Original-patch-by: aaptel <https://github.com/aaptel>
Signed-off-by: 林博仁 <[email protected]>

src/winusb

@@ -107,15 +107,17 @@ init(){
 	source_fs_mountpoint="/media/winusb_source_$(date +%s)_$$"
 	target_fs_mountpoint="/media/winusb_target_$(date +%s)_$$"
 
-	# Commands that needs to be determined in runtime
+	# Parameters that needs to be determined in runtime
 	# due to different names in distributions
 	declare\
 		command_mkdosfs\
-		command_grubinstall
+		command_grubinstall\
+		name_grub_prefix
 
 	if ! check_runtime_dependencies\
 		command_mkdosfs\
-		command_grubinstall; then
+		command_grubinstall\
+		name_grub_prefix; then
 		exit 1
 	fi
 
@@ -191,7 +193,8 @@ init(){
 	install_bootloader_grub\
 		"${target_fs_mountpoint}"\
 		"${target_device}"\
-		"${command_grubinstall}"
+		"${command_grubinstall}"\
+		"${name_grub_prefix}"
 
 	current_state="finished"
 
@@ -312,9 +315,10 @@ process_commandline_parameters(){
 }; declare -fr process_commandline_parameters;
 
 check_runtime_dependencies(){
-	util_check_function_parameters_quantity 2 $#
+	util_check_function_parameters_quantity 3 $#
 	local -n command_mkdosfs_ref="$1"; shift
-	local -n command_grubinstall_ref="$1"
+	local -n command_grubinstall_ref="$1"; shift
+	local -n name_grub_prefix_ref="$1"
 
 	local result="unknown"
 
@@ -357,8 +361,10 @@ check_runtime_dependencies(){
 
 	if command -v 'grub-install' &> /dev/null; then
 		command_grubinstall_ref='grub-install'
+		name_grub_prefix_ref="grub"
 	elif command -v 'grub2-install' &> /dev/null; then
 		command_grubinstall_ref='grub2-install'
+		name_grub_prefix_ref="grub2"
 	else
 		echo_with_color red "${FUNCNAME[0]}: Error: grub-install or grub2-install command not found!" >&2
 		echo_with_color red "${FUNCNAME[0]}: Error: Please make sure that GNU GRUB is properly installed!" >&2
@@ -795,10 +801,11 @@ workaround_support_windows_7_uefi_boot(){
 }; declare -fr workaround_support_windows_7_uefi_boot
 
 install_bootloader_grub(){
-	util_check_function_parameters_quantity 3 "${#}"
+	util_check_function_parameters_quantity 4 "${#}"
 	local -r target_fs_mountpoint="${1}"; shift 1
 	local -r target_device="${1}"; shift 1
-	local -r command_grubinstall="${1}"
+	local -r command_grubinstall="${1}"; shift 1
+	local -r name_grub_prefix="${1}"
 
 	echo_with_color blue "Installing GRUB bootloader for legacy boot support..."
 	"${command_grubinstall}"\
@@ -807,7 +814,7 @@ install_bootloader_grub(){
 		--force "${target_device}"
 
 	echo_with_color blue "Installing grub.cfg..."
-	local -r grub_cfg="${target_fs_mountpoint}/grub/grub.cfg"
+	local -r grub_cfg="${target_fs_mountpoint}/${name_grub_prefix}/grub.cfg"
 	local -r target_fs_uuid=$(\
 		lsblk\
 			--output UUID\