Use a .rvmrc file from a Ruby script - ruby-on-rails

Question

Backgound
A little background to this question first: Ruby on Rails has some security issues as of late. So we need to update the Rails version on our projects. If you have a few, that gets old fast if you do it by hand... So I figured I can create a Thor task for this.
Question
This now works great! BUT! I need to respect the .rvmrc file for each project while installing the new versions of rails. I want this script to be OpenSourced soon, but I want to tacle the problem of not respecting the .rvmrc file first.
So what I need is a way of using the right RVM ruby version/gemset when I change to a directory to update the Rails version.
How is the way for this to be done? Can it be done from the Ruby script in a way so that it works on Mac and Linux, regardless of Shell (found a answer with zsh support, but what about all the other shells out there?)
Quick Example code:
#Scan the base directory down for Gemfiles
gem_files = File.join("**", "Gemfile")
Dir.glob(gem_files){|gemfile|
project_folder = File.dirname(gemfile)
puts "Found Gemfile in #{project_folder}"
Dir.chdir(project_folder) do
#TODO: Respect/load the rvmrc file in this directory
update_gem_file(project_folder) #example
run 'bundle update rails' #<--- needs to be done in the RVM gemset
end
}
Just to give you an idea of what I'm trying to do.
Link to the script on the githubs
The github repo for my script -- Work in Progress!

Answer 1

Check out this project https://github.com/versapay/bundler-auto-update it basically:
Attempt to update every single gem of your Gemfile to its latest patch, minor then major release. Runs a test command to ensure the update succeeded
As for RVM use this simple code:
#Scan the base directory down for Gemfiles
gem_files = File.join("**", "Gemfile")
Dir.glob(gem_files){|gemfile|
project_folder = File.dirname(gemfile)
puts "Found Gemfile in #{project_folder}"
run "rvm in #{project_folder} do bundle-auto-update -c rake spec"
}
You can find more details on scripting with RVM on https://rvm.io

Answer 2

Blindly upgrading Rails is not a good idea. At least run your test suite to ensure nothing breaks. After that you still want to do some QA on the app to make sure you didn't break all the things.
Then, How do you know that the current branch you're updating is actually the main develop branch? Don't you want to create a 'hotfix' branch and apply it to your production and development branches?
But, let's say you did manage to upgrade all your apps, they are still not deployed to production.