internal/system: skip superfluous chmod

A successful chmod clobbers acl mask, breaking the fast path. This
change also fixes the ACL race.

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

1 files changed, 13 insertions, 0 deletions

diff --git a/internal/system/dispatcher_test.go b/internal/system/dispatcher_test.go
index 6ffd0dfa..dd42b965 100644
--- a/internal/system/dispatcher_test.go
+++ b/internal/system/dispatcher_test.go
@@ -2,11 +2,13 @@ package system
 
 import (
 	"io"
+	"io/fs"
 	"log"
 	"os"
 	"reflect"
 	"slices"
 	"testing"
+	"time"
 	"unsafe"
 
 	"hakurei.app/check"
@@ -215,6 +217,17 @@ type kstub struct{ *stub.Stub[syscallDispatcher] }
 
 func (k *kstub) new(f func(k syscallDispatcher)) { k.Helper(); k.New(f) }
 
+// modeFi implements the Mode method of [os.FileInfo].
+type modeFi os.FileMode
+
+func (modeFi) Name() string       { panic("attempting to call Name") }
+func (modeFi) Size() int64        { panic("attempting to call Size") }
+func (modeFi) ModTime() time.Time { panic("attempting to call ModTime") }
+func (modeFi) Sys() any           { panic("attempting to call Sys") }
+
+func (fi modeFi) Mode() fs.FileMode { return fs.FileMode(fi) }
+func (fi modeFi) IsDir() bool       { return fs.FileMode(fi).IsDir() }
+
 func (k *kstub) stat(name string) (fi os.FileInfo, err error) {
 	k.Helper()
 	expect := k.Expects("stat")