Greatly improving the time complexity of `patch-set`

Juxtapose the old code taking 18 seconds to process a patchset of 40K
patches 7 times, versus the new code taking 0.6 seconds.  There's still
room for improvement, though....
More performance improvements for `patch-set`

Old code took 0.6 seconds for 7 processings of 40K patches.  This code,
when those patches are passed in as a single agentset, takes 0.002
seconds.