Deprecate bundle package --all flag

bundler/lib/bundler/cli.rb

@@ -461,6 +461,12 @@ def outdated(*gems)
       bundle without having to download any additional gems.
     D
     def cache
+      SharedHelpers.major_deprecation 2,
+        "The `--all` flag is deprecated because it relies on being " \
+        "remembered across bundler invocations, which bundler will no longer " \
+        "do in future versions. Instead please use `bundle config set cache_all true`, " \
+        "and stop using this flag" if ARGV.include?("--all")
+
       require_relative "cli/cache"
       Cache.new(options).run
     end

bundler/spec/other/major_deprecation_spec.rb

@@ -143,6 +143,28 @@
     pending "should fail with a helpful error", :bundler => "3"
   end
 
+  context "bundle cache --all" do
+    before do
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+        gem "rack"
+      G
+
+      bundle "cache --all", :raise_on_error => false
+    end
+
+    it "should print a deprecation warning", :bundler => "2" do
+      expect(deprecations).to include(
+        "The `--all` flag is deprecated because it relies on being " \
+        "remembered across bundler invocations, which bundler will no " \
+        "longer do in future versions. Instead please use `bundle config set " \
+        "cache_all true`, and stop using this flag"
+      )
+    end
+
+    pending "should fail with a helpful error", :bundler => "3"
+  end
+
   describe "bundle config" do
     describe "old list interface" do
       before do