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.
#if no-windows no-osx
$ mkdir -p xdgconf/hg
$ echo '[ui]' > xdgconf/hg/hgrc
$ echo 'username = foobar' >> xdgconf/hg/hgrc
$ XDG_CONFIG_HOME="`pwd`/xdgconf" ; export XDG_CONFIG_HOME
$ unset HGRCPATH
$ hg config ui.username 2>/dev/null
foobar
#endif