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/init.go

@@ -2,6 +2,7 @@ package container
 
 import (
 	"context"
+	"encoding/gob"
 	"errors"
 	"fmt"
 	"log"
@@ -130,7 +131,7 @@ type initParams struct {
 	Verbose bool
 }
 
-// Init is called by [TryArgv0] if the current process is the container init.
+// Init is called if the current process is the container init.
 func Init(msg message.Msg) { initEntrypoint(direct{}, msg) }
 
 func initEntrypoint(k syscallDispatcher, msg message.Msg) {
@@ -642,18 +643,37 @@ func initEntrypoint(k syscallDispatcher, msg message.Msg) {
 // initName is the prefix used by log.std in the init process.
 const initName = "init"
 
-// TryArgv0 calls [Init] if the last element of argv0 is "init".
-// If a nil msg is passed, the system logger is used instead.
-func TryArgv0(msg message.Msg) {
-	if msg == nil {
-		log.SetPrefix(initName + ": ")
-		log.SetFlags(0)
-		msg = message.New(log.Default())
+var _ = func() struct{} {
+	for _, v := range []any{
+		(*AutoEtcOp)(nil),
+		(*AutoRootOp)(nil),
+		(*BindMountOp)(nil),
+		(*DaemonOp)(nil),
+		(*MkdirOp)(nil),
+		(*MountDevOp)(nil),
+		(*MountOverlayOp)(nil),
+		(*MountProcOp)(nil),
+		(*MountTmpfsOp)(nil),
+		(*RemountOp)(nil),
+		(*SymlinkOp)(nil),
+		(*TmpfileOp)(nil),
+	} {
+		gob.Register(v)
 	}
 
-	if len(os.Args) > 0 && filepath.Base(os.Args[0]) == initName {
+	if len(os.Args) == 1 && filepath.Base(os.Args[0]) == initName {
+		log.SetPrefix(initName + ": ")
+		log.SetFlags(0)
+		msg := message.New(log.Default())
+
 		Init(msg)
 		msg.BeforeExit()
 		os.Exit(0)
 	}
-}
+	return struct{}{}
+}()
+
+// TryArgv0 is a noop.
+//
+// Deprecated: init is now implemented as an import side effect.
+func TryArgv0(_ message.Msg) {}