headssummary: directly feed the function with the 'pushop' object Our goal is to be able to perform the post processing directly into the '_headssummary' function. However before this patch the '_headsummary' function only had access to repo, remote, outgoing while the '_postprocessobsolete' function takes a 'pushop' object. Experience shows that having the 'pushop' object helps extensions so we update '_headssummary' to take a pushop object as argument.

checkheads: gather the postprocessing with other obsolescence specific code We extract this function from the loop and gather it with the rest of the obsolescence specific code. That will help to clarify the move of the whole logic inside the "heads summary" computation.