refactor: move more commands to internal/cmd (#207)

* refactor: move more commands to internal/cmd

Part of https://github.com/ooni/probe/issues/1335.

We would like all commands to be at the same level of engine
rather than inside engine (now that we can do it).

* fix: update .gitignore

* refactor: also move jafar outside engine

* We should be good now?

internal/cmd/jafar/flagx/stringarray.go

@@ -0,0 +1,46 @@
+// Package flagx contains extensions for the standard library
+// flag package. The code is adapted from github.com/m-lab/go and more
+// specifically from <https://git.io/JJ8UA>. This file is licensed under
+// version 2.0 of the Apache License <https://git.io/JJ8Ux>.
+package flagx
+
+import (
+	"fmt"
+	"strings"
+)
+
+// StringArray is a new flag type. It appends the flag parameter to an
+// `[]string` allowing the parameter to be specified multiple times or using ","
+// separated items. Unlike other Flag types, the default argument should almost
+// always be the empty array, because there is no way to remove an element, only
+// to add one.
+type StringArray []string
+
+// Get retrieves the value contained in the flag.
+func (sa StringArray) Get() interface{} {
+	return sa
+}
+
+// Set accepts a string parameter and appends it to the associated StringArray.
+// Set attempts to split the given string on commas "," and appends each element
+// to the StringArray.
+func (sa *StringArray) Set(s string) error {
+	f := strings.Split(s, ",")
+	*sa = append(*sa, f...)
+	return nil
+}
+
+// String reports the StringArray as a Go value.
+func (sa StringArray) String() string {
+	return fmt.Sprintf("%#v", []string(sa))
+}
+
+// Contains returns true when the given value equals one of the StringArray values.
+func (sa StringArray) Contains(value string) bool {
+	for _, v := range sa {
+		if v == value {
+			return true
+		}
+	}
+	return false
+}