chore: remove all deprecated commands

This change removes all deprecated commands. In many cases, users have been warned for a number of releases before the commands have been removed. All commands that were removed have existing alternatives.

docs/appendices/0.20.0-migration-guide.md

@@ -0,0 +1,15 @@
+# 0.20.0 Migration Guide
+
+## Deprecated command removal
+
+The following commands have been deprecated and were removed in this release.
+
+- `apps`: Use `apps:list` instead.
+- `certs`: Use `certs:report` instead.
+- `certs:info`: Use `certs:report` instead.
+- `checks`: Use `checks:report` instead.
+- `docker-options`: Use `docker-options:report` instead.
+- `domains`: Use `domains:report` instead.
+- `plugin`: Use `plugin:list` instead.
+- `proxy`: Use `proxy:report` instead.
+- `trace`: Use `trace:on` or `trace:off` instead.

docs/deployment/zero-downtime-deploys.md

@@ -3,7 +3,6 @@
 > New as of 0.5.0
 
 ```
-checks <app>                             Show zero-downtime status
 checks:disable <app> [process-type(s)]   Disable zero-downtime deployment for all processes (or comma-separated process-type list) ***WARNING: this will cause downtime during deployments***
 checks:enable <app> [process-type(s)]    Enable zero-downtime deployment for all processes (or comma-separated process-type list)
 checks:report [<app>] [<flag>]           Displays a checks report for one or more apps

docs/getting-started/upgrading.md

@@ -51,6 +51,10 @@ Before upgrading, check the migration guides to get comfortable with new feature
 
 - [0.10 Migration Guide](/docs/appendices/0.10.0-migration-guide.md)
 
+### 0.20 Migration Guide
+
+- [0.20 Migration Guide](/docs/appendices/0.20.0-migration-guide.md)
+
 ## Upgrade Instructions
 
 If Dokku was installed via `apt-get install dokku` or `bootstrap.sh` (most common), upgrade with: