v3.2.1

• processx does not depend on assertthat now, and the crayon package
  is now an optional dependency.

v3.2.0

• New process$kill_tree() method, and new cleanup_tree arguments in
  run() and process$new(), to clean up the process tree rooted at a
  processx process. (#139, #143).

• New process$interupt() method to send an interrupt to a process,
  SIGINT on Unix, CTRL+C on Windows (#127).

• New stdin argument in process$new() to support writing to the
  standard input of a process (#27, #114).

• New connections argument in process$new() to support passing extra
  connections to the child process, in addition to the standard streams.

• New poll_connection argument to process$new(), an extra connection
  that can be used to poll the process, even if stdout and stderr are
  not pipes (#125).

• poll() now works with connections objects, and they can be mixed with
  process objects (#121).

• New env argument in run() and process$new(), to set the
  environment of the child process, optionally (#117, #118).

• Removed the $restart() method, because it was less useful than
  expected, and hard to maintain (#116).

• New conn_set_stdout() and conn_set_stderr() to set the standard
  output or error of the calling process.

• New conn_disable_inheritance() to disable stdio inheritance. It is
  suggested that child processes call this immediately after starting, so
  the file handles are not inherited further.

• Fixed a signal handler bug on Unix that marked the process as finished,
  even if it has not (d221aa1).

• Fixed a bug that occasionally caused crashes in wait(), on Unix (#138).

• When run() is interrupted, no error message is printed, just like
  for interruption of R code in general. The thrown condition now also
  has the interrupt class (#148).