docs(cli-sync): Update notes for error handling behavior

Author: tony

docs/cli/sync.md

@@ -4,6 +4,22 @@
 
 # vcspull sync
 
+## Error handling
+
+As of 1.13.x, vcspull will continue to the next repo if an error is encountered when syncing multiple repos.
+
+To imitate the old behavior, use `--exit-on-error` / `-x`:
+
+```console
+$ vcspull sync --exit-on-error grako django
+```
+
+Print traceback for errored repos:
+
+```console
+$ vcspull --log-level DEBUG sync --exit-on-error grako django
+```
+
 ```{eval-rst}
 .. click:: vcspull.cli.sync:sync
     :prog: vcspull sync