Unnecessary files in UM config_files list.

[MartinDix]

The config_files list includes a number of files that the model doesn't actually use. Model configurations would be clearer without the duplicated namelists. See coecms/access-esm#14

[aidanheerdegen]

A simple change would be to move them to the optional_config_files

https://github.com/payu-org/payu/blob/master/payu/models/um.py#L48

[blimlim]

I've had a go at removing the extra files listed here in a branch of payu (also thanks to @jo-basevi for helping get this working). In addition to shortening the um.py config list, I had to remove the following lines:

payu/payu/models/um.py

Lines 144 to 150 in 8a4a1e2

	# The above needs to be done in parexe also.
	# FIXME: a better way to do this or remove.
	parexe = os.path.join(self.work_path, 'parexe')
	for line in fileinput.input(parexe, inplace=True):
	line = line.format(input_path=self.input_paths[0],
	work_path=self.work_path)
	print(line, end='')

As far as I can tell, parexe is empty (at least in the pre-industrial configuration), and it appears to remain so after these lines are run. I just wanted to get confirmation that this would be safe to do, as I'm unsure of the original purpose of parexe.

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Removing the extra config files and running for a few months produces identical simulations to unmodified configurations. The following shows the difference in surface temperature for a simulation with the configuration files removed and one without, on March 31:

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If this sounds ok I'll add pull requests to add the changes to payu and the configurations.

[blimlim]

Closing this issue and have added a new one to remove the extra files in the configurations.