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/engine/shellx/shellx.go

@@ -0,0 +1,66 @@
+// Package shellx contains utilities to run external commands.
+package shellx
+
+import (
+	"errors"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/apex/log"
+	"github.com/google/shlex"
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+)
+
+type runconfig struct {
+	args     []string
+	loginfof func(format string, v ...interface{})
+	name     string
+	stdout   *os.File
+	stderr   *os.File
+}
+
+func run(config runconfig) error {
+	config.loginfof("exec: %s %s", config.name, strings.Join(config.args, " "))
+	cmd := exec.Command(config.name, config.args...)
+	cmd.Stdout = config.stdout
+	cmd.Stderr = config.stderr
+	err := cmd.Run()
+	config.loginfof("exec result: %+v", err)
+	return err
+}
+
+// Run executes the specified command with the specified args
+func Run(name string, arg ...string) error {
+	return run(runconfig{
+		args:     arg,
+		loginfof: log.Log.Infof,
+		name:     name,
+		stdout:   os.Stdout,
+		stderr:   os.Stderr,
+	})
+}
+
+// RunQuiet is like Run but it does not emit any output.
+func RunQuiet(name string, arg ...string) error {
+	return run(runconfig{
+		args:     arg,
+		loginfof: model.DiscardLogger.Infof,
+		name:     name,
+		stdout:   nil,
+		stderr:   nil,
+	})
+}
+
+// RunCommandline is like Run but its only argument is a command
+// line that will be splitted using the google/shlex package
+func RunCommandline(cmdline string) error {
+	args, err := shlex.Split(cmdline)
+	if err != nil {
+		return err
+	}
+	if len(args) < 1 {
+		return errors.New("shellx: no command to execute")
+	}
+	return Run(args[0], args[1:]...)
+}