Wrap node commands with Capistrano

This code is based on what the rvm1-capistrano and capistrano-nvm gems
do, but simplified a bit to take advantage of the `fnm exec` command.

Since we're currently only using Node to precompile the assets, the
important command here is `rake` in order to run the `assets:precompile`
task. I've also included the default commands gems like capistrano-nvm
use because we will add the `npm` command in the near future.

config/deploy.rb

@@ -37,6 +37,16 @@ def main_deploy_server
 
 set :local_user, ENV["USER"]
 
+set :fnm_path, "$HOME/.fnm"
+set :fnm_install_command, "curl -fsSL https://fnm.vercel.app/install | " \
+                          "bash -s -- --install-dir \"#{fetch(:fnm_path)}\""
+set :fnm_setup_command, -> do
+                          "export PATH=\"#{fetch(:fnm_path)}:$PATH\" && " \
+                            "cd #{release_path} && eval \"$(fnm env)\""
+                        end
+set :fnm_install_node_command, -> { "#{fetch(:fnm_setup_command)} && fnm use --install-if-missing" }
+set :fnm_map_bins, %w[node npm rake yarn]
+
 set :puma_conf, "#{release_path}/config/puma/#{fetch(:rails_env)}.rb"
 
 set :delayed_job_workers, 2
@@ -51,6 +61,7 @@ def main_deploy_server
 
   after :updating, "install_ruby"
   after "bundler:install", "install_node"
+  after "bundler:install", "map_node_bins"
 
   after "deploy:migrate", "add_new_settings"
 
@@ -91,10 +102,34 @@ def main_deploy_server
 end
 
 task :install_node do
+  on roles(:app) do
+    with rails_env: fetch(:rails_env) do
+      begin
+        execute fetch(:fnm_install_node_command)
+      rescue SSHKit::Command::Failed
+        begin
+          execute fetch(:fnm_setup_command)
+        rescue SSHKit::Command::Failed
+          execute fetch(:fnm_install_command)
+        else
+          execute "#{fetch(:fnm_install_command)} --skip-shell"
+        end
+
+        execute fetch(:fnm_install_node_command)
+      end
+    end
+  end
+end
+
+task :map_node_bins do
   on roles(:app) do
     within release_path do
       with rails_env: fetch(:rails_env) do
-        execute :rake, "node_manager:install:node"
+        prefix = "#{fetch(:fnm_setup_command)} && fnm exec"
+
+        fetch(:fnm_map_bins).each do |command|
+          SSHKit.config.command_map.prefix[command.to_sym].unshift(prefix)
+        end
       end
     end
   end