Why `If --file or --sync-dir is set, the other must also be set`?

[Araxeus]

• Why can't I just input --file and then the sync dir will automatically be the parent of the file

• Why can't I just input --sync-dir and then the file getting logic will be as usual?

If there isn't some particular reason not to change this behavior, it should pretty easy to do here:

peru/peru/runtime.py

Lines 70 to 79 in 9dbf098

	if explicit_peru_file and explicit_sync_dir:
	self.peru_file = explicit_peru_file
	self.sync_dir = explicit_sync_dir
	elif explicit_peru_file or explicit_sync_dir:
	raise CommandLineError('If the --file or --sync-dir is set, '
	'the other must also be set.')
	else:
	basename = explicit_basename or parser.DEFAULT_PERU_FILE_NAME
	self.peru_file = find_project_file(os.getcwd(), basename)
	self.sync_dir = os.path.dirname(self.peru_file)

I'm willing to give it a go myself if I get a go ahead