Merge same repo once and check fs object is valid (#578)

Co-authored-by: 杨赫然 <heran.yang@seafile.com>

fileserver/utils/utils.go

@@ -0,0 +1,24 @@
+package utils
+
+import (
+	"github.com/google/uuid"
+)
+
+func IsValidUUID(u string) bool {
+	_, err := uuid.Parse(u)
+	return err == nil
+}
+
+func IsObjectIDValid(objID string) bool {
+	if len(objID) != 40 {
+		return false
+	}
+	for i := 0; i < len(objID); i++ {
+		c := objID[i]
+		if (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') {
+			continue
+		}
+		return false
+	}
+	return true
+}