container/init: split setup ops into individual files

This significantly increases readability.

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

container/initmkdir.go

@@ -0,0 +1,34 @@
+package container
+
+import (
+	"encoding/gob"
+	"fmt"
+	"os"
+	"syscall"
+)
+
+func init() { gob.Register(new(MkdirOp)) }
+
+// Mkdir appends an [Op] that creates a directory in the container filesystem.
+func (f *Ops) Mkdir(name *Absolute, perm os.FileMode) *Ops {
+	*f = append(*f, &MkdirOp{name, perm})
+	return f
+}
+
+// MkdirOp creates a directory at container Path with permission bits set to Perm.
+type MkdirOp struct {
+	Path *Absolute
+	Perm os.FileMode
+}
+
+func (m *MkdirOp) early(*setupState) error { return nil }
+func (m *MkdirOp) apply(*setupState) error {
+	if m.Path == nil {
+		return syscall.EBADE
+	}
+	return wrapErrSelf(os.MkdirAll(toSysroot(m.Path.String()), m.Perm))
+}
+
+func (m *MkdirOp) Is(op Op) bool  { vm, ok := op.(*MkdirOp); return ok && m == vm }
+func (*MkdirOp) prefix() string   { return "creating" }
+func (m *MkdirOp) String() string { return fmt.Sprintf("directory %q perm %s", m.Path, m.Perm) }