add changelog for locking refactor

changelog/unreleased/pull-4709

@@ -0,0 +1,10 @@
+Bugfix: Correct `--no-lock` handling of `ls` and `tag` command
+
+The `ls` command never locked the repository. This has been fixed. The old
+behavior is still supported using `ls --no-lock`. The latter invocation also
+works with older restic versions.
+
+The `tag` command erroneously accepted the `--no-lock` command. The command
+now always requires an exclusive lock.
+
+https://github.com/restic/restic/pull/4709