Check FSL scripts for branches

[Lestropie]

The current pruning process implicitly assumes that the example data on which the external software scripts are run are sufficient to explore the full set of commands that may be invoked by those scripts. If however there is any branching logic within those scripts that results in a specific command being invoked only in certain circumstances, then it is possible that a command may be pruned that is in fact requisite for certain types of data input.

While such absences should be reported by users over time, it would be preferable to do an initial interrogation of the code within these scripts, and cross-reference with the results of the minify pruning process. If such code branches can be found, then the test data should be augmented to ensure that such commands are utilised at least once during the battery of tests.

[Lestropie]

Note: as an example, 775b803 was necessitated due to a code branch in standard_space_roi, with 5ttgen fsl following different branches depending on use of the -nocrop option.