Starting with Tools R12,the SDK Manager offers a slightly better way
to update the SDK from command-line.

PrevIoUsly the “android update sdk --no-ui” command already allowed
one to update from the command-line,but it had the annoying tendency
of installing every single platform or add-on. There are now 30 or
more packages available on the SDK repository,including 12 platforms;
that’s a lot to download when most people only need the most recent
platform. Starting with R12,you can use combine new things:

• “android list sdk” will connect to the remote repository and list all the
  packages available with an index number.

• “android update sdk --no-ui”
  accepts a “--filter” argument that can take a package index,or a
  category name.

Here’s an example in action:

There’s still room for improvement,notably in a future release we’ll work on the first install case and making the update smarter at figuring out what to get.