docs: document no-deps and what it's good for

disko

@@ -35,6 +35,11 @@ Options:
   where to mount the device tree (default: /mnt)
 * --dry-run
   just show the path to the script instead of running it
+* --no-deps
+  avoid adding another dependency closure to an in-memory installer
+    recommended when using flake attributes variant where the flake's
+    nixpkgs and the nixpkgs version of the in-memory installer may diverge
+    requires all necessary dependencies to be available in the environment
 * --debug
   run with set -x
 USAGE