Add upgrade fixing before I forget it again

README.md

@@ -39,6 +39,26 @@ Fully automated luxury Nextcloud via docker-swarm.
 
 `abra app run --user www-data YOURAPPDOMAIN app occ app:update --all`
 
+## How do I fix a Nextcloud version snafu?
+
+`Exception: Updates between multiple major versions and downgrades are unsupported.`
+
+Solution:
+
+- Look at log files to determine the old Nextcloud version
+- Change your local `~/.abra/recipes/nextcloud/compose.yml` to the highest minor
+    version in the old version -- e.g. choose `22.2.5` for `22`, if you're
+    upgrading to `23`.
+- Then, do one of (both bad):
+  1. `abra app deploy --chaos ...`, then `app run` to go in and manually lower the version number in PHP (shell in, `apt install vim-core && vi version.php`), then try `php ./occ upgrade`
+  2. `abra app undeploy ...`, `abra volume rm`, CAREFULLY only choose the volume
+     ENDING `_nextcloud`, then `abra app deploy --chaos ...`, then edit the
+     `compose.yml` to add `entrypoint: ['tail', '-f', '/dev/null']` to `app`,
+     then `app deploy --chaos` again, then `app run --user=www-data ... app bash` to get in and run `./occ maintenance:repair`, and `./occ upgrade`. 
+- Change `compose.yml` to the new version number; `git checkout compose.yml`
+- `abra app deploy --force`
+- This wasn't even multiplle major versions was it 😾
+
 ## How do I integrate with Keycloak SSO?
 
 Use [this plugin](https://github.com/pulsejet/nextcloud-oidc-login). Unlike the plugin it's forked from, there is no configuration UI, so you'll need to edit `/var/www/html/config/config.php`: