Prepend .kamal/bin to PATH during hook execution

lib/kamal/cli/base.rb

@@ -154,6 +154,7 @@ def run_hook(hook, **extra_details)
           end
 
           with_env KAMAL.hook.env(**details, **extra_details) do
+            prepend_kamal_bin_to_path
             KAMAL.with_verbosity(hook_verbosity) do
               run_locally do
                 execute *KAMAL.hook.run(hook)
@@ -219,6 +220,12 @@ def with_env(env)
         ENV.update(current_env)
       end
 
+      def prepend_kamal_bin_to_path
+        kamal_bin = File.expand_path(".kamal/bin")
+        ENV["PATH"] = "#{kamal_bin}#{File::PATH_SEPARATOR}#{ENV["PATH"]}" \
+          if Dir.exist?(kamal_bin)
+      end
+
       def ensure_docker_installed
         run_locally do
           begin

test/cli/main_test.rb

@@ -785,6 +785,53 @@ class CliMainTest < CliTestCase
     end
   end
 
+  test ".kamal/bin is prepended to PATH by prepend_kamal_bin_to_path" do
+    Dir.mktmpdir do |tmpdir|
+      Dir.chdir(tmpdir) do
+        FileUtils.mkdir_p(".kamal/bin")
+
+        cli = Kamal::Cli::Base.allocate
+        original_path = ENV["PATH"]
+        kamal_bin = File.expand_path(".kamal/bin")
+
+        cli.send(:prepend_kamal_bin_to_path)
+        assert ENV["PATH"].start_with?("#{kamal_bin}#{File::PATH_SEPARATOR}"),
+          "Expected PATH to start with #{kamal_bin}, got: #{ENV["PATH"]}"
+
+        ENV["PATH"] = original_path
+      end
+    end
+  end
+
+  test ".kamal/bin is not added to PATH when directory is absent" do
+    Dir.mktmpdir do |tmpdir|
+      Dir.chdir(tmpdir) do
+        cli = Kamal::Cli::Base.allocate
+        original_path = ENV["PATH"]
+
+        cli.send(:prepend_kamal_bin_to_path)
+        assert_equal original_path, ENV["PATH"],
+          "PATH should be unchanged when .kamal/bin does not exist"
+      end
+    end
+  end
+
+  test "with_env does not prepend .kamal/bin to PATH" do
+    Dir.mktmpdir do |tmpdir|
+      Dir.chdir(tmpdir) do
+        FileUtils.mkdir_p(".kamal/bin")
+
+        cli = Kamal::Cli::Base.allocate
+        original_path = ENV["PATH"]
+
+        cli.send(:with_env, { "FOO" => "bar" }) do
+          assert_equal original_path, ENV["PATH"],
+            "with_env should not modify PATH"
+        end
+      end
+    end
+  end
+
   test "upgrade rolling" do
     invoke_options = { "config_file" => "test/fixtures/deploy_with_accessories.yml", "skip_hooks" => false, "confirmed" => true, "rolling" => false }
     Kamal::Cli::Main.any_instance.expects(:invoke).with("kamal:cli:proxy:upgrade", [], invoke_options).times(4)