Add a pre-init hook

The hook is run before the environment is loaded or the config is
parsed.

This makes it a bit of a special case - it doesn't have the usual
KAMAL_XYZ environment variables, as we haven't parsed the config.

The use case for this is to do auth checking or setup. So for example
we can confirm you are logged in to a secret manager, and then you
can directly call it to load your secrets in the .kamal/.env file
using .dotenv's
[command substitution](https://github.com/bkeepers/dotenv?tab=readme-ov-file#command-substitution).

lib/kamal/cli/base.rb

@@ -22,9 +22,21 @@ module Kamal::Cli
 
     class_option :skip_hooks, aliases: "-H", type: :boolean, default: false, desc: "Don't run hooks"
 
+    @@ran_pre_init_hook = false
+    class << self
+      def ran_pre_init_hook
+        @@ran_pre_init_hook
+      end
+
+      def ran_pre_init_hook=(value)
+        @@ran_pre_init_hook = value
+      end
+    end
+
     def initialize(*)
       super
       @original_env = ENV.to_h.dup
+      run_pre_init_hook
       load_env
       initialize_commander(options_with_subcommand_class_options)
     end
@@ -176,8 +188,23 @@ module Kamal::Cli
         end
       end
 
+      def run_pre_init_hook
+        unless self.class.ran_pre_init_hook
+          hook = "pre-init"
+          if run_hook?(hook)
+            say "Running the #{hook} hook...", :magenta
+            run_locally do
+              execute *Kamal::Hooks.file(hook), verbosity: :debug
+            rescue SSHKit::Command::Failed => e
+              raise HookError.new("Hook `#{hook}` failed:\n#{e.message}")
+            end
+          end
+          self.class.ran_pre_init_hook = true
+        end
+      end
+
       def run_hook(hook, **extra_details)
-        if !options[:skip_hooks] && KAMAL.hook.hook_exists?(hook)
+        if run_hook?(hook)
           details = { hosts: KAMAL.hosts.join(","), command: command, subcommand: subcommand }
 
           say "Running the #{hook} hook...", :magenta
@@ -189,6 +216,10 @@ module Kamal::Cli
         end
       end
 
+      def run_hook?(hook)
+        !options[:skip_hooks] && Kamal::Hooks.exists?(hook)
+      end
+
       def on(*args, &block)
         if !KAMAL.connected?
           run_hook "pre-connect"

lib/kamal/commands/hook.rb

@@ -1,14 +1,5 @@
 class Kamal::Commands::Hook < Kamal::Commands::Base
   def run(hook, **details)
-    [ hook_file(hook), env: tags(**details).env ]
+    [ Kamal::Hooks.file(hook), env: tags(**details).env ]
   end
-
-  def hook_exists?(hook)
-    Pathname.new(hook_file(hook)).exist?
-  end
-
-  private
-    def hook_file(hook)
-      File.join(config.hooks_path, hook)
-    end
 end

lib/kamal/configuration.rb

@@ -7,7 +7,7 @@ require "erb"
 require "net/ssh/proxy/jump"
 
 class Kamal::Configuration
-  delegate :service, :image, :labels, :stop_wait_time, :hooks_path, to: :raw_config, allow_nil: true
+  delegate :service, :image, :labels, :stop_wait_time, to: :raw_config, allow_nil: true
   delegate :argumentize, :optionize, to: Kamal::Utils
 
   attr_reader :destination, :raw_config
@@ -208,10 +208,6 @@ class Kamal::Configuration
     end
   end
 
-  def hooks_path
-    raw_config.hooks_path || ".kamal/hooks"
-  end
-
   def asset_path
     raw_config.asset_path
   end

lib/kamal/configuration/docs/configuration.yml

@@ -74,10 +74,6 @@ env:
 # To configure this, set the path to the assets:
 asset_path: /path/to/assets
 
-# Path to hooks, defaults to `.kamal/hooks`
-# See https://kamal-deploy.org/docs/hooks for more information
-hooks_path: /user_home/kamal/hooks
-
 # Require destinations
 #
 # Whether deployments require a destination to be specified, defaults to `false`