Passing parameters to Capistrano - deployment

Question

I'm looking into the possibility of using Capistrano as a generic deploy solution. By "generic", I mean not-rails. I'm not happy with the quality of the documentation I'm finding, though, granted, I'm not looking at the ones that presume you are deploying rails. So I'll just try to hack up something based on a few examples, but there are a couple of problems I'm facing right from the start.
My problem is that cap deploy doesn't have enough information to do anything. Importantly, it is missing the tag for the version I want to deploy, and this has to be passed on the command line.
The other problem is how I specify my git repository. Our git server is accessed by SSH on the user's account, but I don't know how to change deploy.rb to use the user's id as part of the scm URL.
So, how do I accomplish these things?
Example
I want to deploy the result of the first sprint of the second release. That's tagged in the git repository as r2s1. Also, let's say user "johndoe" gets the task of deploying the system. To access the repository, he has to use the URL johndoe#gitsrv.domain:app. So the remote URL for the repository depends on the user id.
The command lines to get the desired files would be these:
git clone johndoe#gitsrv.domain:app
cd app
git checkout r2s1

Answer 1

Update: For Capistrano 3, see scieslak's answer below.
Has jarrad has said, capistrano-ash is a good basic set of helper modules to deploy other project types, though it's not required as at the end of the day. It's just a scripting language and most tasks are done with the system commands and end up becoming almost shell script like.
To pass in parameters, you can set the -s flag when running cap to give you a key value pair. First create a task like this.
desc "Parameter Testing"
task :parameter do
puts "Parameter test #{branch} #{tag}"
end
Then start your task like so.
cap test:parameter -s branch=master -s tag=1.0.0
For the last part. I would recommend setting up passwordless access using ssh keys to your server. But if you want to take it from the current logged in user. You can do something like this.
desc "Parameter Testing"
task :parameter do
system("whoami", user)
puts "Parameter test #{user} #{branch} #{tag}"
end
UPDATE: Edited to work with the latest versions of Capistrano. The configuration array is no longer available.
Global Parameters: See comments Use set :branch, fetch(:branch, 'a-default-value') to use parameters globally. (And pass them with -S instead.)

Answer 2

Update. Regarding passing parameters to Capistrano 3 task only.
I know this question is quite old but still pops up first on Google when searching for passing parameters to Capistrano task. Unfortunately, the fantastic answer provided by Jamie Sutherland is no longer valid with Capistrano 3. Before you waste your time trying it out except the results to be like below:
cap test:parameter -s branch=master
outputs :
cap aborted!
OptionParser::AmbiguousOption: ambiguous option: -s
OptionParser::InvalidOption: invalid option: s
and
cap test:parameter -S branch=master
outputs:
invalid option: -S
The valid answers for Capistrano 3 provided by #senz and Brad Dwyer you can find by clicking this gold link:
Capistrano 3 pulling command line arguments
For completeness see the code below to find out about two option you have.
1st option:
You can iterate tasks with the key and value as you do with regular hashes:
desc "This task accepts optional parameters"
task :task_with_params, :first_param, :second_param do |task_name, parameter|
run_locally do
puts "Task name: #{task_name}"
puts "First parameter: #{parameter[:first_param]}"
puts "Second parameter: #{parameter[:second_param]}"
end
end
Make sure there is no space between parameters when you call cap:
cap production task_with_params[one,two]
2nd option:
While you call any task, you can assign environmental variables and then call them from the code:
set :first_param, ENV['first_env'] || 'first default'
set :second_param, ENV['second_env'] || 'second default'
desc "This task accepts optional parameters"
task :task_with_env_params do
run_locally do
puts "First parameter: #{fetch(:first_param)}"
puts "Second parameter: #{fetch(:second_param)}"
end
end
To assign environmental variables, call cap like bellow:
cap production task_with_env_params first_env=one second_env=two
Hope that will save you some time.

Answer 3

I'd suggest to use ENV variables.
Somethings like this (command):
$ GIT_REPO="johndoe#gitsrv.domain:app" GIT_BRANCH="r2s1" cap testing
Cap config:
#deploy.rb:
task :testing, :roles => :app do
puts ENV['GIT_REPO']
puts ENV['GIT_BRANCH']
end
And take a look at the https://github.com/capistrano/capistrano/wiki/2.x-Multistage-Extension, may be this approach will be useful for you as well.

Answer 4

As Jamie already showed, you can pass parameters to tasks with the -s flag. I want to show you how you additionally can use a default value.
If you want to work with default values, you have to use fetch instead of ||= or checking for nil:
namespace :logs do
task :tail do
file = fetch(:file, 'production') # sets 'production' as default value
puts "I would use #{file}.log now"
end
end
You can either run this task by (uses the default value production for file)
$ cap logs:tail
or (uses the value cron for file
$ cap logs:tail -s file=cron

Answer 5

Check out capistrano-ash for a library that helps with non-rails deployment. I use it to deploy a PyroCMS app and it works great.
Here is a snippet from my Capfile for that project:
# deploy from git repo
set :repository, "git#git.mygitserver.com:mygitrepo.git"
# tells cap to use git
set :scm, :git
I'm not sure I understand the last two parts of the question. Provide some more detail and I'd be happy to help.
EDIT after example given:
set :repository, "#{scm_user}#gitsrv.domain:app"
Then each person with deploy priveledges can add the following to their local ~/.caprc file:
set :scm_user, 'someuser'