Absolute path to executable

[jmgate]

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Currently the get_*_command_line_invocation() methods start the command line with the executable, but it's only the name of the script being run. For replicability's sake, this should really be the absolute path to the script executed, otherwise two different users could be running scripts of the same name in different locations and they'd be different scripts, and therefore behave differently, leading to confusing that this package is intended to address.