Deprecate `bundle install --force`

Instead of hard erroring, deprecate the `--force` flag on bundler 2 to
better teach users about the replacement.

Before:

$ bundle install --force
Unknown switches '--force'

After:

$ bundle install --force
[DEPRECATED FOR 2.0] The `--force` option has been renamed to `--redownload`
Could not locate Gemfile # or whatever the expected behavior for --redownload is

2 files changed, 12 insertions, 2 deletions

diff --git a/lib/bundler/cli.rb b/lib/bundler/cli.rb
index f692ae5f13..73f4e1bf9d 100644
--- a/lib/bundler/cli.rb
+++ b/lib/bundler/cli.rb
@@ -206,8 +206,7 @@ module Bundler
       "Do not attempt to fetch gems remotely and use the gem cache instead"
     deprecated_option "no-cache", :type => :boolean, :banner =>
       "Don't update the existing gem cache."
-    method_option "redownload", :type => :boolean, :aliases =>
-      [Bundler.feature_flag.forget_cli_options? ? nil : "--force"].compact, :banner =>
+    method_option "redownload", :type => :boolean, :aliases => "--force", :banner =>
       "Force downloading every gem."
     deprecated_option "no-prune", :type => :boolean, :banner =>
       "Don't remove stale gems from the cache."
@@ -230,6 +229,7 @@ module Bundler
       "Include gems that are part of the specified named group."
     map "i" => "install"
     def install
+      SharedHelpers.major_deprecation(2, "The `--force` option has been renamed to `--redownload`") if ARGV[1] == "--force"
       require "bundler/cli/install"
       Bundler.settings.temporary(:no_install => false) do
         Install.new(options.dup).run
diff --git a/spec/install/redownload_spec.rb b/spec/install/redownload_spec.rb
index 626a4a8e9f..d6fcc9c2b8 100644
--- a/spec/install/redownload_spec.rb
+++ b/spec/install/redownload_spec.rb
@@ -60,11 +60,21 @@ RSpec.describe "bundle install" do
     it_behaves_like "an option to force redownloading gems" do
       let(:flag) { "force" }
     end
+
+    it "shows a deprecation" do
+      bundle! :install, :force => true
+      expect(out).to include "[DEPRECATED FOR 2.0] The `--force` option has been renamed to `--redownload`"
+    end
   end
 
   describe "with --redownload" do
     it_behaves_like "an option to force redownloading gems" do
       let(:flag) { "redownload" }
     end
+
+    it "does not show a deprecation" do
+      bundle! :install, :redownload => true
+      expect(out).not_to include "[DEPRECATED FOR 2.0] The `--force` option has been renamed to `--redownload`"
+    end
   end
 end