'board details' shows info on selected options

This allows to show which option is selected with defaults or with
different FQBNs.

For example:

    $ arduino-cli board details arduino:avr:nano
    Board name: Arduino Nano

    Option:     Processor                         cpu
                ATmega328P                      ✔ cpu=atmega328
                ATmega328P (Old Bootloader)       cpu=atmega328old
                ATmega168                         cpu=atmega168

or:

    $ arduino-cli board details arduino:avr:nano:cpu=atmega328old
    Board name: Arduino Nano

    Option:     Processor                         cpu
                ATmega328P                        cpu=atmega328
                ATmega328P (Old Bootloader)     ✔ cpu=atmega328old
                ATmega168                         cpu=atmega168

commands/board/details.go

@@ -21,6 +21,7 @@ import (
 	"encoding/json"
 	"os"
 
+	"github.com/arduino/arduino-cli/arduino/cores"
 	"github.com/arduino/arduino-cli/output"
 
 	"github.com/arduino/arduino-cli/commands"
@@ -42,8 +43,13 @@ func initDetailsCommand() *cobra.Command {
 
 func runDetailsCommand(cmd *cobra.Command, args []string) {
 	pm := commands.InitPackageManager()
-	fqbnIn := args[0]
-	board, err := pm.FindBoardWithFQBN(fqbnIn)
+	fqbn, err := cores.ParseFQBN(args[0])
+	if err != nil {
+		formatter.PrintError(err, "Error parsing fqbn")
+		os.Exit(commands.ErrBadArgument)
+	}
+
+	_, _, board, _, _, err := pm.ResolveFQBN(fqbn)
 	if err != nil {
 		formatter.PrintError(err, "Error loading board data")
 		os.Exit(commands.ErrBadArgument)
@@ -53,17 +59,22 @@ func runDetailsCommand(cmd *cobra.Command, args []string) {
 	details.Name = board.Name()
 	details.ConfigOptions = []*boardConfigOption{}
 	options := board.GetConfigOptions()
+	t := true
 	for _, option := range options.Keys() {
 		configOption := &boardConfigOption{}
 		configOption.Option = option
 		configOption.OptionLabel = options.Get(option)
+		selected, hasSelected := fqbn.Configs.GetOk(option)
+
 		values := board.GetConfigOptionValues(option)
 		for i, value := range values.Keys() {
 			configValue := &boardConfigValue{}
-			if i == 0 {
-				t := true
-				configValue.Default = &t
+			if hasSelected && value == selected {
+				configValue.Selected = &t
+			} else if !hasSelected && i == 0 {
+				configValue.Selected = &t
 			}
+
 			configValue.Value = value
 			configValue.ValueLabel = values.Get(value)
 			configOption.Values = append(configOption.Values, configValue)
@@ -89,7 +100,7 @@ type boardConfigOption struct {
 type boardConfigValue struct {
 	Value      string
 	ValueLabel string
-	Default    *bool `json:",omitempty"`
+	Selected   *bool `json:",omitempty"`
 }
 
 func (details *boardDetails) EmitJSON() string {
@@ -103,12 +114,23 @@ func (details *boardDetails) EmitJSON() string {
 
 func (details *boardDetails) EmitTerminal() string {
 	table := output.NewTable()
-	table.AddRow("Board name:", output.Red(details.Name))
+	table.AddRow("Board name:", details.Name)
 	table.SetColumnWidthMode(1, output.Average)
 	for _, option := range details.ConfigOptions {
-		table.AddRow("Option:", option.OptionLabel)
+		table.AddRow()
+		table.AddRow("Option:",
+			option.OptionLabel,
+			"", option.Option)
 		for _, value := range option.Values {
-			table.AddRow("", value.ValueLabel, option.Option+"="+value.Value)
+			if value.Selected != nil {
+				table.AddRow("",
+					output.Green(value.ValueLabel),
+					output.Green("✔"), output.Green(option.Option+"="+value.Value))
+			} else {
+				table.AddRow("",
+					value.ValueLabel,
+					"", option.Option+"="+value.Value)
+			}
 		}
 	}
 	return table.Render()