Add tool for converting gadget3 ICs to EAGLE ICs in HDF format

[j-davies-astro]

I've been using this script to convert gadget3 ICs (as outputted by genetIC) to EAGLE-compatible HDF5 ICs for a long while now, and I thought it might be useful to include it in the tools here. I was spurred on to do this because Gandhali may need to write something similar, or adapt this script, to create ICs compatible with IllustrisTNG.

[cphyc]

It is common to put the docstring at the very beginning of the script file rather than after the imports.

[cphyc]

There is actually a special argument file type to handle files

Suggested change

	type=str,
	type=argparse.FileType(mode="br"),

Note that you need to open it in binary format for FortranFile to be happy.

[cphyc]

Assuming you use the trick bellow, this'll have to be changed into

Suggested change

	def ics2hdf(ics_file):
	raw_ics = os.path.abspath(ics_file)
	# Do quick checks to make sure input is valid
	assert os.path.isfile(raw_ics),'Input ICs file does not exist.'
	assert raw_ics.split('.')[-1] == 'gadget3','Input ICs not valid. Please input GADGET3 binary ICs (.gadget3)'
	out_ics = raw_ics[:-7] + 'hdf5'
	print('Reading binary file '+raw_ics)
	# Open the FORTRAN unformatted binary ICs
	f = FortranFile(raw_ics, 'r')
	def ics2hdf(ics_file):
	assert ics_file.name.split('.')[-1] == 'gadget3', 'Input ICs not valid. Please input GADGET3 binary ICs (.gadget3)'
	out_ics = raw_ics.name[:-7] + "hdf5"
	print(f"Reading binary file {raw_ics}")
	# Open the FORTRAN unformatted binary ICs
	f = FortranFile(ics_file, 'r')