Q:

Is there a reference document that lists and describes all available variables in Capistrano?

I can usually google around and find this kind of thing but I just can't find this one.
What I'm looking for is a list and description for all the variables that I can set in my deploy.rb file in a Rails 3 app with Capistrano 2.
I've found and read these:
https://github.com/leehambley/capistrano-handbook/blob/master/index.markdown
https://github.com/capistrano/capistrano/wiki/2.x-Significant-Configuration-Variables
http://theadmin.org/articles/2010/06/24/capistrano-variables/
But there are some other variables I'm aware of such as :scm_command, and :local_scm_command (found them here in SO) that are not listed there.
I also took a look at gems/capistrano/lib/capistrano/recipes/deploy.rb but the list is still incomplete.
Where is the complete list of capistrano variables?

A:

Fun story, you can set whichever variables you want.  The list of variables that actually need to be set and are used depends on the recipes you are using for deployment. When you're using your own custom recipes, you can set and use whatever variables you want. For instance, a particularly ugly part of my deploy config requires knowing which unicorn pid/config each app is using (as there are multiple unicorns handling utility things on this server in addition to the main app), so I have to 
set :unicorn_pid, '/var/run/unicorn/rails.pid'

in one of the app config tasks.
Good luck!

