Is there any way to set different SSH keys to ruby-git gem configuration on the fly, so I can work with different private repos?

What I've done is working well, but it works with one SSH key only.

I have created /ruby_git.sh in the root folder of my Rails app:

#!/bin/bash
exec /usr/bin/ssh -o StrictHostKeyChecking=no -i ./certs/private_key "$@"

I have created /certs/private_key with my SSH key:

-----BEGIN OPENSSH PRIVATE KEY-----
...
-----END OPENSSH PRIVATE KEY-----

I have created /initializers/git_init.rb:

Git.configure do |config|
  config.git_ssh = Rails.root.join("ruby_git.sh").to_s
end

I have also tried another approach, to create custom sh scripts and SSH private key files for each repo in runtime and delete them after use. But this seems to alter Git globally, so the next thread/session inherits the new Git config:

# @repo_id, @ssh_url and @private_key are instance variables set
# based on the repo that we try to interact with

cert_path   = Rails.root.join("git_config", "certs", @repo_id).to_s
config_path = Rails.root.join("git_config", "configs", "#{@repo_id}.sh").to_s
git_config  = "#!\/bin\/bash\n\nexec \/usr\/bin\/ssh -o StrictHostKeyChecking=no -i #{cert_path} \"$@\""

File.open(config_path, "w") { |f|
  f.write(git_config)
}

File.open(cert_path, "w") { |f|
  f.write(@private_key)
}

File.chmod(0755, config_path)
File.chmod(0600, cert_path)

Git.init

Git.configure { |config|
  config.git_ssh = config_path
}

Git.ls_remote(@ssh_url)

FileUtils.remove_entry(cert_path)
FileUtils.remove_entry(config_path)

I tried to work with ~/.ssh/config. The following is working, but it does not mach my needs.

Host github.com
  PreferredAuthentications publickey
  IdentityFile /home/ubuntu/.ssh/repo_1_private_key

I'm working with multiple repos. SSH pair created for each of them. Public part used as a deploy key. No users.

I need to measure one repo/key pair from another and do not let ssh have access to other keys or iterate through them.

something like

Host github.com/organization_1/repo_1
  PreferredAuthentications publickey
  IdentityFile /home/ubuntu/.ssh/repo_1_private_key

Host github.com/organization_2/repo_2
  PreferredAuthentications publickey
  IdentityFile /home/ubuntu/.ssh/repo_2_private_key

is not working because github.com/organization/repo doesn't mach with github.com host and configuration is skipped when tried to git clone git@github.com:organization/repo.git.