container: enter init path early

There is generally no use case where any setup is required before init, and requiring the explicit function call is error-prone and unnecessary. It also causes trouble with packages using a similar trick. This change moves argv0 check early and makes it an import side effect. The stub will be removed in v0.5.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/container_test.go

@@ -37,9 +37,6 @@ import (
 
 // Note: this package requires cgo, which is unavailable in the Go playground.
 func Example() {
-	// Must be called early if the current process starts containers.
-	container.TryArgv0(nil)
-
 	// Configure the container.
 	z := container.New(context.Background(), nil)
 	z.Hostname = "hakurei-example"
@@ -876,8 +873,6 @@ var (
 var helperCommands []func(c command.Command)
 
 func TestMain(m *testing.M) {
-	container.TryArgv0(nil)
-
 	if os.Getenv(envDoCheck) == "1" {
 		c := command.New(os.Stderr, log.Printf, "helper", func(args []string) error {
 			log.SetFlags(0)