migration docs

docs/markdown/migration/1.4_1.5.md

@@ -1,5 +1,9 @@
 # Migration from `1.4` to `1.5`
 
+## ⚠️ Important notes
+
+The way snapshots are referenced in the `restore` and `prune` commands has been changed. Before they were referenced by the path. Now every backup is tagged and those tags are then referenced in the cli. This means that when running restore and forget commands old backups are not taken into account anymore.
+
 ## Config files
 
 - The config file now required to have a version number. This has to be added with `version: 2` at the root.
@@ -8,6 +12,15 @@
 
 See detailed instructions below.
 
+## Config Version
+
+```yaml
+version: 2 # Added
+
+backends:
+  # ...
+```
+
 ## Hooks
 
 Since `1.5` multiple sources for a location are possible.