add alias `u` to the update command

doc/03-cli.md

@@ -115,7 +115,7 @@ resolution.
   requirements and force the installation even if the local machine does not
   fulfill these. See also the [`platform`](06-config.md#platform) config option.
 
-## update
+## update / u
 
 In order to get the latest versions of the dependencies and to update the
 `composer.lock` file, you should use the `update` command. This command is also

src/Composer/Command/UpdateCommand.php

@@ -34,7 +34,7 @@ class UpdateCommand extends BaseCommand
     {
         $this
             ->setName('update')
-            ->setAliases(array('upgrade'))
+            ->setAliases(array('u', 'upgrade'))
             ->setDescription('Upgrades your dependencies to the latest version according to composer.json, and updates the composer.lock file.')
             ->setDefinition(array(
                 new InputArgument('packages', InputArgument::IS_ARRAY | InputArgument::OPTIONAL, 'Packages that should be updated, if not provided all packages are.'),