Undocumented in source.

auto helpText = q"EOS Synopsis: tsv-split [options] [file...] Split input lines into multiple output files. There are three modes of operation: * Fixed number of lines per file (--l|lines-per-file NUM): Each input block of NUM lines is written to a new file. Similar to Unix 'split'. * Random assignment (--n|num-files NUM): Each input line is written to a randomly selected output file. Random selection is from NUM files. * Random assignment by key (--n|num-files NUM, --k|key-fields FIELDS): Input lines are written to output files using fields as a key. Each unique key is randomly assigned to one of NUM output files. All lines with the same key are written to the same file. By default, files are written to the current directory and have names of the form 'part_NNN<suffix>', with 'NNN' being a number and <suffix> being the extension of the first input file. If the input file is 'file.txt', the names will take the form 'part_NNN.txt'. The output directory and file names are customizable. Fields are specified using field number or field name. Field names require that the input file has a header line. Use '--help-verbose' for more detailed information. Options: EOS";