system/tmpfiles: do not fail for smaller files

The limit is meant to be an upper bound. Handle EOF and print verbose message for it instead of failing.

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

system/dispatcher.go

@@ -1,12 +1,20 @@
 package system
 
 import (
+	"io"
+	"io/fs"
 	"os"
 
 	"hakurei.app/system/acl"
 	"hakurei.app/system/dbus"
 )
 
+type osFile interface {
+	Name() string
+	io.Writer
+	fs.File
+}
+
 // syscallDispatcher provides methods that make state-dependent system calls as part of their behaviour.
 // syscallDispatcher is embedded in [I], so all methods must be unexported.
 type syscallDispatcher interface {
@@ -15,6 +23,10 @@ type syscallDispatcher interface {
 	// just synchronising access is not enough, as this is for test instrumentation.
 	new(f func(k syscallDispatcher))
 
+	// stat provides os.Stat.
+	stat(name string) (os.FileInfo, error)
+	// open provides [os.Open].
+	open(name string) (osFile, error)
 	// mkdir provides os.Mkdir.
 	mkdir(name string, perm os.FileMode) error
 	// chmod provides os.Chmod.
@@ -48,6 +60,8 @@ type direct struct{}
 
 func (k direct) new(f func(k syscallDispatcher)) { go f(k) }
 
+func (k direct) stat(name string) (os.FileInfo, error)     { return os.Stat(name) }
+func (k direct) open(name string) (osFile, error)          { return os.Open(name) }
 func (k direct) mkdir(name string, perm os.FileMode) error { return os.Mkdir(name, perm) }
 func (k direct) chmod(name string, mode os.FileMode) error { return os.Chmod(name, mode) }
 func (k direct) link(oldname, newname string) error        { return os.Link(oldname, newname) }