BF: according to Mark Jenkinson and FAQ all --long options should use = before the value



References:
ML: https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind1308&L=FSL&F=&S=&P=158682
FAQ: https://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FSL%20FAQ