Document the new migration tool

docs/reference/cli/config.md

@@ -26,7 +26,7 @@ clients:
   # ...
 ```
 
-## `config generate`
+## `config generate [--synapse-config <synapse-config>] [--output <output>]`
 
 Generate a sample configuration file.
 It generates random signing keys (`.secrets.keys`) and the cookie encryption secret (`.secrets.encryption`).
@@ -38,6 +38,10 @@ INFO generate:rsa: mas_config::oauth2: Done generating RSA key
 INFO generate:ecdsa: mas_config::oauth2: Done generating ECDSA key
 ```
 
+The `--synapse-config` option can be used to migrate over configuration options from an existing Synapse configuration.
+
+The `--output` option can be used to specify the output file. If not specified, the output will be written to stdout.
+
 ## `config sync [--prune] [--dry-run]`
 
 Synchronize the configuration with the database.
@@ -52,4 +56,4 @@ INFO cli.config.sync: Updating provider provider.id=01H3FDH2XZJS8ADKRGWM84PZTY
 INFO cli.config.sync: Adding provider provider.id=01H3FDH2XZJS8ADKRGWM84PZTF
 INFO cli.config.sync: Deleting client client.id=01GFWRB9MYE0QYK60NZP2YF905
 INFO cli.config.sync: Updating client client.id=01GFWRB9MYE0QYK60NZP2YF904
-```
+```

docs/reference/cli/syn2mas.md

@@ -0,0 +1,29 @@
+# `syn2mas`
+
+Tool to import data from an existing Synapse homeserver into MAS.
+
+Global options:
+- `--config <config>`: Path to the MAS configuration file.
+- `--help`: Print help.
+- `--synapse-config <synapse-config>`: Path to the Synapse configuration file.
+- `--synapse-database-uri <synapse-database-uri>`: Override the Synapse database URI.
+
+## `syn2mas check`
+
+Check the setup for potential problems before running a migration
+
+```console
+$ mas-cli syn2mas check --config mas_config.yaml --synapse-config homeserver.yaml
+```
+
+## `syn2mas migrate [--dry-run]`
+
+Migrate data from the homeserver to MAS.
+
+The `--dry-run` option will perform a dry-run of the migration, which is safe to run without stopping Synapse.
+It will perform a full data migration, but then empty the MAS database at the end to roll back.
+
+
+```console
+$ mas-cli syn2mas migrate --config mas_config.yaml --synapse-config homeserver.yaml
+```