Can Drush update custom modules? I'm currently using Drush Make to pull custom modules, installation profile, and various other modules/libraries when I provision a new Drupal site.

What I'd love is if I could use drush upc to update my custom modules.  I'm not sure if this is possible if I provide some magic meta data to drush or include my .git with a specified remote host.

My understanding is that Drush leverages the update status module in core for this functionality so this may not necessarily be a Drush specific issue.

Any help or suggestions on where to look would be appreciated.
As you said, Drush relies on the update status module of Drupal to find code updates.  If you wanted to use this mechanism for your own custom modules, you would have to make a server that had clones of the d.o modules you used, since pm-updatecode works with a single update server, and also has the same xml data structure for the releases of your custom modules.

There are two easier solutions:


Publish your custom modules on drupal.org - very easy, and a great option if your modules can be shared openly.
Just check out your custom modules from git; after running pm-updatecode, iterate over each custom module and do a 'git pull'.


The later could be integrated with drush pm-updatecode, either as a post-updatecode hook or as a feature request submitted in the Drush issue queue (patches welcome).