test: add SetWD function to packerCommand

For some tests we may need Packer to run in another directory than the
one we're invoking the tests from, so we add a new function to the
packerCommand structure to change that.

test/commands_test.go

@@ -15,6 +15,7 @@ type packerCommand struct {
 	env        map[string]string
 	stderr     *strings.Builder
 	stdout     *strings.Builder
+	workdir    string
 	err        error
 }
 
@@ -42,6 +43,12 @@ func (pc *packerCommand) NoVerbose() *packerCommand {
 	return pc
 }
 
+// SetWD changes the directory Packer is invoked from
+func (pc *packerCommand) SetWD(dir string) *packerCommand {
+	pc.workdir = dir
+	return pc
+}
+
 // UsePluginDir sets the plugin directory in the environment to `dir`
 func (pc *packerCommand) UsePluginDir(dir string) *packerCommand {
 	return pc.AddEnv("PACKER_PLUGIN_PATH", dir)
@@ -76,6 +83,10 @@ func (pc *packerCommand) doRun() {
 	cmd.Stdout = pc.stdout
 	cmd.Stderr = pc.stderr
 
+	if pc.workdir != "" {
+		cmd.Dir = pc.workdir
+	}
+
 	pc.err = cmd.Run()
 }