commands: rename plugin to execute

The plugin and plugins command had a name that was close, and while
plugin is not supposed to be directly called by Packer users, this could
happen by accident while trying to execute packer plugins subcommands,
and when it does, the error messages are far from explicit, so unless
they understand what Packer is doing here, they'll likely be lost.

To reduce the risk of confusion, we rename the command to run packer
embedded components as execute.

command/plugin.go → command/execute.go

@@ -36,7 +36,7 @@ import (
 	windowsshellprovisioner "github.com/hashicorp/packer/provisioner/windows-shell"
 )
 
-type PluginCommand struct {
+type ExecuteCommand struct {
 	Meta
 }
 
@@ -75,13 +75,13 @@ var Datasources = map[string]packersdk.Datasource{
 
 var pluginRegexp = regexp.MustCompile("packer-(builder|post-processor|provisioner|datasource)-(.+)")
 
-func (c *PluginCommand) Run(args []string) int {
+func (c *ExecuteCommand) Run(args []string) int {
 	// This is an internal call (users should not call this directly) so we're
 	// not going to do much input validation. If there's a problem we'll often
 	// just crash. Error handling should be added to facilitate debugging.
 	log.Printf("args: %#v", args)
 	if len(args) != 1 {
-		c.Ui.Error("Wrong number of args")
+		c.Ui.Error("Wrong number of args - this command is not meant tobe manually invoked.")
 		return 1
 	}
 
@@ -136,9 +136,9 @@ func (c *PluginCommand) Run(args []string) int {
 	return 0
 }
 
-func (*PluginCommand) Help() string {
+func (*ExecuteCommand) Help() string {
 	helpText := `
-Usage: packer plugin PLUGIN
+Usage: packer execute PLUGIN
 
   Runs an internally-compiled version of a plugin from the packer binary.
 
@@ -148,6 +148,6 @@ Usage: packer plugin PLUGIN
 	return strings.TrimSpace(helpText)
 }
 
-func (c *PluginCommand) Synopsis() string {
+func (c *ExecuteCommand) Synopsis() string {
 	return "internal plugin command"
 }

commands.go

@@ -29,6 +29,12 @@ func init() {
 			}, nil
 		},
 
+		"execute": func() (cli.Command, error) {
+			return &command.ExecuteCommand{
+				Meta: *CommandMeta,
+			}, nil
+		},
+
 		"fix": func() (cli.Command, error) {
 			return &command.FixCommand{
 				Meta: *CommandMeta,
@@ -59,12 +65,6 @@ func init() {
 			}, nil
 		},
 
-		"plugin": func() (cli.Command, error) {
-			return &command.PluginCommand{
-				Meta: *CommandMeta,
-			}, nil
-		},
-
 		"plugins": func() (cli.Command, error) {
 			return &command.PluginsCommand{
 				Meta: *CommandMeta,

config.go

@@ -153,7 +153,7 @@ func (c *config) discoverInternalComponents() error {
 	for builder := range command.Builders {
 		builder := builder
 		if !c.Plugins.Builders.Has(builder) {
-			bin := fmt.Sprintf("%s%splugin%spacker-builder-%s",
+			bin := fmt.Sprintf("%s%sexecute%spacker-builder-%s",
 				packerPath, PACKERSPACE, PACKERSPACE, builder)
 			c.Plugins.Builders.Set(builder, func() (packersdk.Builder, error) {
 				return c.Plugins.Client(bin).Builder()
@@ -164,7 +164,7 @@ func (c *config) discoverInternalComponents() error {
 	for provisioner := range command.Provisioners {
 		provisioner := provisioner
 		if !c.Plugins.Provisioners.Has(provisioner) {
-			bin := fmt.Sprintf("%s%splugin%spacker-provisioner-%s",
+			bin := fmt.Sprintf("%s%sexecute%spacker-provisioner-%s",
 				packerPath, PACKERSPACE, PACKERSPACE, provisioner)
 			c.Plugins.Provisioners.Set(provisioner, func() (packersdk.Provisioner, error) {
 				return c.Plugins.Client(bin).Provisioner()
@@ -175,7 +175,7 @@ func (c *config) discoverInternalComponents() error {
 	for postProcessor := range command.PostProcessors {
 		postProcessor := postProcessor
 		if !c.Plugins.PostProcessors.Has(postProcessor) {
-			bin := fmt.Sprintf("%s%splugin%spacker-post-processor-%s",
+			bin := fmt.Sprintf("%s%sexecute%spacker-post-processor-%s",
 				packerPath, PACKERSPACE, PACKERSPACE, postProcessor)
 			c.Plugins.PostProcessors.Set(postProcessor, func() (packersdk.PostProcessor, error) {
 				return c.Plugins.Client(bin).PostProcessor()
@@ -186,7 +186,7 @@ func (c *config) discoverInternalComponents() error {
 	for dataSource := range command.Datasources {
 		dataSource := dataSource
 		if !c.Plugins.DataSources.Has(dataSource) {
-			bin := fmt.Sprintf("%s%splugin%spacker-datasource-%s",
+			bin := fmt.Sprintf("%s%sexecute%spacker-datasource-%s",
 				packerPath, PACKERSPACE, PACKERSPACE, dataSource)
 			c.Plugins.DataSources.Set(dataSource, func() (packersdk.Datasource, error) {
 				return c.Plugins.Client(bin).Datasource()

main.go

@@ -265,7 +265,7 @@ func wrappedMain() int {
 		Args:         args,
 		Autocomplete: true,
 		Commands:     Commands,
-		HelpFunc:     excludeHelpFunc(Commands, []string{"plugin"}),
+		HelpFunc:     excludeHelpFunc(Commands, []string{"execute"}),
 		HelpWriter:   os.Stdout,
 		Name:         "packer",
 		Version:      version.Version,