Fix "log -L" command line parsing bugs.
* tr/line-log:
t4211: fix incorrect rebase at
f8395edc (range-set: satisfy non-empty ranges invariant)
line-log: fix "log -LN" crash when N is last line of file
range-set: satisfy non-empty ranges invariant
t4211: demonstrate crash when first -L encountered is empty range
t4211: demonstrate empty -L range crash
range-set: fix sort_and_merge_range_set() corner case bug