Allow negative numbers to be used in specifying edit_history commands. * libinterp/interpfcn/oct-hist.cc(mk_tmp_hist_file): Add total number of history commands to negative history numbers to wraparound to positive history number specification. * libinterp/interpfcn/oct-hist.cc(Fedit_history, Frun_history): Update docstrings to describe new behavior. * libinterp/interpfcn/oct-hist.cc(do_edit_history): Comment out first variable to stop unused warning during compilation.

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