Replace .env* with .kamal/env*

By default look for the env file in .kamal/env to avoid clashes with
other tools using .env.

For now we'll still load .env and issue a deprecation warning, but in
future we'll stop reading those.

lib/kamal/cli/base.rb

@@ -37,9 +37,22 @@ module Kamal::Cli
 
       def load_env
         if destination = options[:destination]
-          Dotenv.load(".env.#{destination}", ".env")
+          if File.exist?(".kamal/env.#{destination}") || File.exist?(".kamal/env")
+            Dotenv.load(".kamal/env.#{destination}", ".kamal/env")
+          else
+            loading_files = [ (".env" if File.exist?(".env")), (".env.#{destination}" if File.exist?(".env.#{destination}")) ].compact
+            if loading_files.any?
+              warn "Loading #{loading_files.join(" and ")} from the project root, use .kamal/env* instead"
+              Dotenv.load(".env.#{destination}", ".env")
+            end
+          end
         else
-          Dotenv.load(".env")
+          if File.exist?(".kamal/env")
+            Dotenv.load(".kamal/env")
+          elsif File.exist?(".env")
+            warn "Loading .env from the project root is deprecated, use .kamal/env instead"
+            Dotenv.load(".env")
+          end
         end
       end
 

lib/kamal/cli/main.rb

@@ -183,11 +183,25 @@ class Kamal::Cli::Main < Kamal::Cli::Base
   option :skip_push, aliases: "-P", type: :boolean, default: false, desc: "Skip .env file push"
   def envify
     if destination = options[:destination]
-      env_template_path = ".env.#{destination}.erb"
-      env_path          = ".env.#{destination}"
+      env_template_path = ".kamal/env.#{destination}.erb"
+      env_path          = ".kamal/env.#{destination}"
     else
-      env_template_path = ".env.erb"
-      env_path          = ".env"
+      env_template_path = ".kamal/env.erb"
+      env_path          = ".kamal/env"
+    end
+
+    unless Pathname.new(File.expand_path(env_template_path)).exist?
+      if destination = options[:destination]
+        env_template_path = ".env.#{destination}.erb"
+        env_path          = ".env.#{destination}"
+      else
+        env_template_path = ".env.erb"
+        env_path          = ".env"
+      end
+
+      if Pathname.new(File.expand_path(env_template_path)).exist?
+        warn "Loading #{env_template_path} from the project root is deprecated, use .kamal/env[.<DESTINATION>].erb instead"
+      end
     end
 
     if Pathname.new(File.expand_path(env_template_path)).exist?