Add new `prune` command as discussed in: #6863 #5633

Usage: vagrant box prune [options]

Options:

    -p, --provider PROVIDER          The specific provider type for the boxes to destroy.
    -n, --dry-run                    Only print the boxes that would be removed.
        --name NAME                  The specific box name to check for outdated versions.
    -f, --force                      Destroy without confirmation even when box is in use.
    -h, --help                       Print this help

plugins/commands/box/command/prune.rb

@@ -0,0 +1,128 @@
+require 'optparse'
+
+module VagrantPlugins
+  module CommandBox
+    module Command
+      class Prune < Vagrant.plugin("2", :command)
+        def execute
+          options = {}
+          options[:force] = false
+          options[:dry_run] = false
+
+          opts = OptionParser.new do |o|
+            o.banner = "Usage: vagrant box prune [options]"
+            o.separator ""
+            o.separator "Options:"
+            o.separator ""
+
+            o.on("-p PROVIDER", "--provider PROVIDER", String, "The specific provider type for the boxes to destroy.") do |p|
+              options[:provider] = p
+            end
+
+            o.on("-n", "--dry-run", "Only print the boxes that would be removed.") do |f|
+              options[:dry_run] = f
+            end
+
+            o.on("--name NAME", String, "The specific box name to check for outdated versions.") do |name|
+              options[:name] = name
+            end
+
+            o.on("-f", "--force", "Destroy without confirmation even when box is in use.") do |f|
+              options[:force] = f
+            end
+          end
+
+          # Parse the options
+          argv = parse_options(opts)
+          return if !argv
+
+          boxes = @env.boxes.all.sort
+          if boxes.empty?
+            return @env.ui.warn(I18n.t("vagrant.commands.box.no_installed_boxes"), prefix: false)
+          end
+
+          delete_oldest_boxes(boxes, options[:provider], options[:force], options[:name], options[:dry_run])
+
+          # Success, exit status 0
+          0
+        end
+
+        private
+
+        def delete_oldest_boxes(boxes, only_provider, skip_confirm, only_name, dry_run)
+          # Find the longest box name
+          longest_box = boxes.max_by { |x| x[0].length }
+          longest_box_length = longest_box[0].length
+
+          # Hash map to keep track of newest versions
+          newest_boxes = Hash.new
+
+          # First find the newest version for every installed box
+          boxes.each do |name, version, provider|
+            next if only_provider and only_provider != provider.to_s
+            next if only_name and only_name != name
+
+            # Nested to make sure it works for boxes with different providers
+            if newest_boxes.has_key?(name)
+              if newest_boxes[name].has_key?(provider)
+                saved = Gem::Version.new(newest_boxes[name][provider])
+                current = Gem::Version.new(version)
+                if current > saved
+                  newest_boxes[name][provider] = version
+                end
+              else
+                newest_boxes[name][provider] = version
+              end
+            else
+              newest_boxes[name] = Hash.new
+              newest_boxes[name][provider] = version
+            end
+          end
+
+          @env.ui.info("The following boxes will be kept...");
+          newest_boxes.each do |name, providers|
+            providers.each do |provider, version|
+              @env.ui.info("#{name.ljust(longest_box_length)} (#{provider}, #{version})")
+
+              @env.ui.machine("box-name", name)
+              @env.ui.machine("box-provider", provider)
+              @env.ui.machine("box-version", version)
+            end
+          end
+
+          @env.ui.info("", prefix: false)
+          @env.ui.info("Checking for older boxes...");
+
+          # Track if we removed anything so the user can be informed
+          removed_any_box = false
+          boxes.each do |name, version, provider|
+            next if !newest_boxes.has_key?(name) or !newest_boxes[name].has_key?(provider)
+
+            current = Gem::Version.new(version)
+            saved = Gem::Version.new(newest_boxes[name][provider])
+            if current < saved
+              removed_any_box = true
+
+              # Use the remove box action
+              if dry_run
+                @env.ui.info("Would remove #{name} #{provider} #{version}")
+              else
+                @env.action_runner.run(Vagrant::Action.action_box_remove, {
+                    box_name: name,
+                    box_provider: provider,
+                    box_version: version,
+                    force_confirm_box_remove: skip_confirm,
+                    box_remove_all_versions: false,
+                })
+              end
+            end
+          end
+
+          if !removed_any_box
+            @env.ui.info("No old versions of boxes to remove...");
+          end
+        end
+      end
+    end
+  end
+end

plugins/commands/box/command/root.rb

@@ -34,6 +34,11 @@ module VagrantPlugins
             Remove
           end
 
+          @subcommands.register(:prune) do
+            require_relative "prune"
+            Prune
+          end
+
           @subcommands.register(:repackage) do
             require File.expand_path("../repackage", __FILE__)
             Repackage