eval input changes

[cleverca22]

http://hydra.earthtools.ca/eval/7093#tabs-inputs

with some jobsets, the result of the eval is rarely changing(only things impacting 1 package), even when a large number of commits are happening

and with the old hydra logic, it will show all commits between the last eval and the current eval, including stuff that had no effect on the eval

but hercules could record the commit of every eval that had no differences detected, and could then cut the commit range down to just the poll interval