Add optional command extensions

README.md

@@ -165,6 +165,29 @@ in Dosh's host config:
 dosh import-ssh palav homelab
 ```
 
+Optional command extensions are just config-side startup shortcuts; Dosh has no
+compile-time dependency on the tools they run. For example, to make a separately
+installed server-side `tm` dashboard easy to open:
+
+```toml
+# ~/.config/dosh/client.toml
+[extensions.tm]
+command = "tm {args}"
+description = "Open the server-side tmux dashboard"
+```
+
+Then `dosh palav tm` sends `tm`, and `dosh palav tm dosh` sends `tm 'dosh'`.
+Remove that table to remove the integration. Hosts can override or opt out:
+
+```toml
+# ~/.config/dosh/hosts.toml
+[palav.extensions.tm]
+command = "/opt/tm/bin/tm {args}"
+
+[other-host.extensions.tm]
+disabled = true
+```
+
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