71: Allow user to change config options at runtime

There is a LoadConf and a LoadConfFromFile.
LoadConfFromFile reads the iniFile into memory and and calls
LoadConf, which executes the old parsing commands from
LoadConf (old func).

The remaining of the LoadConfFromFile is the same as the old OldConf.

commands/set.go

@@ -0,0 +1,69 @@
+package commands
+
+import (
+	"errors"
+	"strings"
+
+	"git.sr.ht/~sircmpwn/aerc/widgets"
+
+	"github.com/go-ini/ini"
+)
+
+type Set struct{}
+
+func setUsage() string {
+	return "set <category>.<option> <value>"
+}
+
+func init() {
+	register(Set{})
+}
+
+func (_ Set) Aliases() []string {
+	return []string{"set"}
+
+}
+
+func (_ Set) Complete(aerc *widgets.Aerc, args []string) []string {
+	return nil
+}
+
+func SetCore(aerc *widgets.Aerc, args []string) error {
+	if len(args) != 3 {
+		return errors.New("Usage: " + setUsage())
+	}
+
+	config := aerc.Config()
+
+	parameters := strings.Split(args[1], ".")
+
+	if len(parameters) != 2 {
+		return errors.New("Usage: " + setUsage())
+	}
+
+	category := parameters[0]
+	option := parameters[1]
+	value := args[2]
+
+	new_file := ini.Empty()
+
+	section, err := new_file.NewSection(category)
+
+	if err != nil {
+		return nil
+	}
+
+	if _, err := section.NewKey(option, value); err != nil {
+		return err
+	}
+
+	if err := config.LoadConfig(new_file); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (_ Set) Execute(aerc *widgets.Aerc, args []string) error {
+	return SetCore(aerc, args)
+}