Options to "git pack-objects" that take numeric values like
--window and --depth should not accept negative values; the input
validation has been tightened.
* jk/pack-objects-negative-options-fix:
pack-objects: clamp negative depth to 0
t5316: check behavior of pack-objects --depth=0
pack-objects: clamp negative window size to 0
t5300: check that we produced expected number of deltas
t5300: modernize basic tests