command: add --release-only flag to validate/build

Since we added the capability for the plugin discovery to ignore
installed pre-releases of plugins, we give that capacity to the validate
and build commands, through a new command-line flag: release-only.

command/build.go

@@ -86,6 +86,11 @@ func writeDiags(ui packersdk.Ui, files map[string]*hcl.File, diags hcl.Diagnosti
 }
 
 func (c *BuildCommand) RunContext(buildCtx context.Context, cla *BuildArgs) int {
+	// Set the release only flag if specified as argument
+	//
+	// This deactivates the capacity for Packer to load development binaries.
+	c.CoreConfig.Components.PluginConfig.ReleasesOnly = cla.ReleaseOnly
+
 	packerStarter, ret := c.GetConfig(&cla.MetaArgs)
 	if ret != 0 {
 		return ret

command/cli.go

@@ -90,6 +90,9 @@ func (ba *BuildArgs) AddFlagSets(flags *flag.FlagSet) {
 	flags.Var(flagOnError, "on-error", "")
 
 	flags.BoolVar(&ba.MetaArgs.WarnOnUndeclaredVar, "warn-on-undeclared-var", false, "Show warnings for variable files containing undeclared variables.")
+
+	flags.BoolVar(&ba.ReleaseOnly, "ignore-prerelease-plugins", false, "Disable the loading of prerelease plugin binaries (x.y.z-<prerelease-name>.")
+
 	ba.MetaArgs.AddFlagSets(flags)
 }
 
@@ -100,6 +103,7 @@ type BuildArgs struct {
 	Color, TimestampUi, MachineReadable bool
 	ParallelBuilds                      int64
 	OnError                             string
+	ReleaseOnly                         bool
 }
 
 func (ia *InitArgs) AddFlagSets(flags *flag.FlagSet) {
@@ -142,6 +146,7 @@ func (va *ValidateArgs) AddFlagSets(flags *flag.FlagSet) {
 	flags.BoolVar(&va.SyntaxOnly, "syntax-only", false, "check syntax only")
 	flags.BoolVar(&va.NoWarnUndeclaredVar, "no-warn-undeclared-var", false, "Ignore warnings for variable files containing undeclared variables.")
 	flags.BoolVar(&va.EvaluateDatasources, "evaluate-datasources", false, "evaluate datasources for validation (HCL2 only, may incur costs)")
+	flags.BoolVar(&va.ReleaseOnly, "ignore-prerelease-plugins", false, "Disable the loading of prerelease plugin binaries (x.y.z-<prerelease-name>.")
 
 	va.MetaArgs.AddFlagSets(flags)
 }
@@ -151,6 +156,7 @@ type ValidateArgs struct {
 	MetaArgs
 	SyntaxOnly, NoWarnUndeclaredVar bool
 	EvaluateDatasources             bool
+	ReleaseOnly                     bool
 }
 
 func (va *InspectArgs) AddFlagSets(flags *flag.FlagSet) {

command/validate.go

@@ -48,6 +48,11 @@ func (c *ValidateCommand) ParseArgs(args []string) (*ValidateArgs, int) {
 }
 
 func (c *ValidateCommand) RunContext(ctx context.Context, cla *ValidateArgs) int {
+	// Set the release only flag if specified as argument
+	//
+	// This deactivates the capacity for Packer to load development binaries.
+	c.CoreConfig.Components.PluginConfig.ReleasesOnly = cla.ReleaseOnly
+
 	// By default we want to inform users of undeclared variables when validating but not during build time.
 	cla.MetaArgs.WarnOnUndeclaredVar = true
 	if cla.NoWarnUndeclaredVar {