Add overload option for the CLI

README.md

@@ -223,7 +223,7 @@ You can use the `-t` or `--template` flag on the dotenv cli to create a template
 ```shell
 $ dotenv -t .env
 ```
-A template will be created in your working directory named `{FINAME}.template`. So in the above example, it would create a `.env.template` file. 
+A template will be created in your working directory named `{FINAME}.template`. So in the above example, it would create a `.env.template` file.
 
 The template will contain all the environment variables in your `.env` file but with their values set to the variable names.
 
@@ -233,7 +233,7 @@ S3_BUCKET=YOURS3BUCKET
 SECRET_KEY=YOURSECRETKEYGOESHERE
 ```
 
-Would become 
+Would become
 
 ```shell
 # .env.template
@@ -247,6 +247,11 @@ Personally, I prefer to commit the `.env` file with development-only settings. T
 
 By default, it **won't** overwrite existing environment variables as dotenv assumes the deployment environment has more knowledge about configuration than the application does. To overwrite existing environment variables you can use `Dotenv.overload`.
 
+You can also use the `-o` or `--overload` flag on the dotenv cli to override existing `ENV` variables.
+```shell
+$ dotenv -o -f ".env.local,.env"
+```
+
 ## Contributing
 
 If you want a better idea of how dotenv works, check out the [Ruby Rogues Code Reading of dotenv](https://www.youtube.com/watch?v=lKmY_0uY86s).

lib/dotenv/cli.rb

@@ -7,18 +7,19 @@ module Dotenv
   # The CLI is a class responsible of handling all the command line interface
   # logic.
   class CLI
-    attr_reader :argv, :filenames
+    attr_reader :argv, :filenames, :overload
 
     def initialize(argv = [])
       @argv = argv.dup
       @filenames = []
+      @overload = false
     end
 
     def run
       parse_argv!(@argv)
 
       begin
-        Dotenv.load!(*@filenames)
+        load_dotenv(@overload, @filenames)
       rescue Errno::ENOENT => e
         abort e.message
       else
@@ -36,8 +37,17 @@ def parse_argv!(argv)
       @filenames
     end
 
+    def load_dotenv(overload, filenames)
+      if overload
+        Dotenv.overload!(*filenames)
+      else
+        Dotenv.load!(*filenames)
+      end
+    end
+
     def add_options(parser)
       add_files_option(parser)
+      add_overload_option(parser)
       add_help_option(parser)
       add_version_option(parser)
       add_template_option(parser)
@@ -49,6 +59,12 @@ def add_files_option(parser)
       end
     end
 
+    def add_overload_option(parser)
+      parser.on("-o", "--overload", "override existing ENV variables") do
+        @overload = true
+      end
+    end
+
     def add_help_option(parser)
       parser.on("-h", "--help", "Display help") do
         puts parser