By default when you run a dump with ‘mysqldump’ the date of the dump is appended to the file, e.g.:

jj5@love:~/desktop/experiment$ udiff *
--- dbt__jj_dev_1__svn_jdrepo.1.sql     2019-06-11 18:11:13.267758230 +1000
+++ dbt__jj_dev_1__svn_jdrepo.2.sql     2019-06-11 18:12:03.856075974 +1000
@@ -32,4 +32,4 @@
 /*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
 /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

--- Dump completed on 2019-06-10 21:59:44
+-- Dump completed on 2019-06-10 12:06:49

This causes dumps for a single database that has not changed to have two dumps which differ. It’s better to have dumps from the same unchanged database to be the same. To facilitate that add the –skip-dump-date option when running ‘mysqldump’.

See here for the back-story.