old_contents: # Copyright 2015 The Bazel Authors. All rights reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  def _impl(ctx):
      dir = ctx.label.name
      jar = ctx.outputs.jar
  
      cmd = [
          "touch %s" % (jar.path),
      ]
  
      ctx.action(
          outputs = [jar],
          progress_message = "Generating empty jar for %s" % ctx.attr.name,
          command = ";\n".join(cmd),
      )
  
  empty_jar = rule(
      implementation = _impl,
      outputs = {"jar": "%{name}.jar"},
  )
  
new_contents: # Copyright 2015 The Bazel Authors. All rights reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  def _impl(ctx):
      dir = ctx.label.name
      jar = ctx.outputs.jar
  
      cmd = [
          "mkdir readme && touch readme/README && jar cf %s readme/README" % (jar.path),
      ]
  
      ctx.action(
          outputs = [jar],
          progress_message = "Generating empty jar for %s" % ctx.attr.name,
          command = ";\n".join(cmd),
      )
  
  empty_jar = rule(
      implementation = _impl,
      outputs = {"jar": "%{name}.jar"},
  )
  
subject: Put a file in the empty jar