create alias instruction

internal/instruction/alias.go

@@ -0,0 +1,37 @@
+package instruction
+
+import (
+	"strings"
+)
+
+type alias struct {
+	raw string
+	// Name of the alias
+	Name string
+	// Value to resolve to
+	Value string
+}
+
+func (d *alias) Raw() string { return strings.Join([]string{"alias", d.raw}, " ") }
+
+func (d *alias) Build(_args string) error {
+
+	// 1. extract action fields ()
+	split := strings.SplitN(_args, " ", 2)
+
+	// 2. check syntax
+	if len(split) != 2 {
+		return ErrInvalidSyntax
+	}
+
+	d.Name = split[0]
+	d.Value = split[1]
+	d.raw = _args
+
+	return nil
+}
+
+func (d alias) Exec(ctx ExecutionContext) ([]byte, error) {
+	ctx.Alias[d.Name] = d.Value
+	return nil, nil
+}

internal/instruction/reader.go

@@ -40,6 +40,10 @@ func Parse(raw string) (T, error) {
 		i := &set{}
 		err := i.Build(split[1])
 		return i, err
+	case "alias":
+		i := &alias{}
+		err := i.Build(split[1])
+		return i, err
 	default:
 		return nil, ErrUnknownInstruction
 	}