add changes to maintain perms and owner of logfile

lumberjack_test.go

@@ -493,7 +493,6 @@ func TestRotate(t *testing.T) {
 	existsWithLen(filename2, n, t)
 	existsWithLen(filename, 0, t)
 	fileCount(dir, 2, t)
-
 	newFakeTime()
 
 	err = l.Rotate()
@@ -574,6 +573,43 @@ localtime = true`[1:]
 	equals(0, len(md.Undecoded()), t)
 }
 
+func TestMaintainMode(t *testing.T) {
+	currentTime = fakeTime
+	dir := makeTempDir("TestMaintainMode", t)
+	defer os.RemoveAll(dir)
+
+	filename := logFile(dir)
+
+	mode := os.FileMode(0770)
+	f, err := os.OpenFile(filename, os.O_CREATE|os.O_RDWR, mode)
+	isNil(err, t)
+	f.Close()
+
+	l := &Logger{
+		Filename:   filename,
+		MaxBackups: 1,
+		MaxSize:    100, // megabytes
+	}
+	defer l.Close()
+	b := []byte("boo!")
+	n, err := l.Write(b)
+	isNil(err, t)
+	equals(len(b), n, t)
+
+	newFakeTime()
+
+	err = l.Rotate()
+	isNil(err, t)
+
+	filename2 := backupFile(dir)
+	info, err := os.Stat(filename)
+	isNil(err, t)
+	info2, err := os.Stat(filename2)
+	isNil(err, t)
+	equals(mode, info.Mode(), t)
+	equals(mode, info2.Mode(), t)
+}
+
 // makeTempDir creates a file with a semi-unique name in the OS temp directory.
 // It should be based on the name of the test, to keep parallel tests from
 // colliding, and must be cleaned up after the test is finished.