Add in a server exec command for running ad-hoc commands directly on the server

lib/kamal/cli/app.rb

@@ -106,7 +106,7 @@ class Kamal::Cli::App < Kamal::Cli::Base
     end
   end
 
-  desc "exec [CMD]", "Execute a custom command on servers (use --help to show options)"
+  desc "exec [CMD]", "Execute a custom command on servers within the app container (use --help to show options)"
   option :interactive, aliases: "-i", type: :boolean, default: false, desc: "Execute command over ssh for an interactive shell (use for console/bash)"
   option :reuse, type: :boolean, default: false, desc: "Reuse currently running container instead of starting a new one"
   def exec(cmd)

lib/kamal/cli/server.rb

@@ -1,4 +1,26 @@
 class Kamal::Cli::Server < Kamal::Cli::Base
+  desc "exec", "Run a custom command on the server(use --help to show options)"
+  option :interactive, type: :boolean, aliases: "-i", default: false, desc: "Run the command interactively(use for console/bash)"
+  def exec(cmd)
+    hosts = KAMAL.hosts | KAMAL.accessory_hosts
+
+    case
+    when options[:interactive]
+      host = hosts.first
+
+      say "Running '#{cmd}' on #{host} interactively...", :magenta
+
+      run_locally { exec KAMAL.server.run_over_ssh(cmd, host: host) }
+    else
+      say "Running '#{cmd}' on #{hosts.join(', ')}...", :magenta
+
+      on(hosts) do |host|
+        execute *KAMAL.auditor.record("Executed cmd '#{cmd}' on #{host}"), verbosity: :debug
+        puts_by_host host, capture_with_info(cmd)
+      end
+    end
+  end
+
   desc "bootstrap", "Set up Docker to run Kamal apps"
   def bootstrap
     missing = []

test/cli/server_test.rb

@@ -1,6 +1,20 @@
 require_relative "cli_test_case"
 
 class CliServerTest < CliTestCase
+  test "running a command with exec" do
+    SSHKit::Backend::Abstract.any_instance.stubs(:capture)
+    .with("date", verbosity: 1)
+    .returns("Today")
+
+    hosts = "1.1.1.1".."1.1.1.4"
+    run_command("exec", "date").tap do |output|
+      hosts.map do |host|
+        assert_match "Running 'date' on #{hosts.to_a.join(', ')}...", output
+        assert_match "App Host: #{host}\nToday", output
+      end
+    end
+  end
+
   test "bootstrap already installed" do
     SSHKit::Backend::Abstract.any_instance.expects(:execute).with(:docker, "-v", raise_on_non_zero_exit: false).returns(true).at_least_once
     SSHKit::Backend::Abstract.any_instance.expects(:execute).with(:mkdir, "-p", ".kamal").returns("").at_least_once