diff: reordering and renaming of variables

diff: reordering and renaming of variables

function                                             old     new   delta
diff_main                                            843     848      +5
get_recursive_dirlist                                177     180      +3
add_to_dirlist                                        64      66      +2
change                                               329     326      -3
files_differ                                         182     176      -6
diffreg                                             1823    1808     -15
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(add/remove: 0/0 grow/shrink: 3/3 up/down: 10/-24)            Total: -14 bytes