phases: apply similar early filtering to advanceboundary
advanceboundary is called the push's unbundle (but not the other unbundle) so
advanceboundary did not show up the profile I looked at so far.
We start with simple pre-filtering to avoid doing any work if we don't needs
too.
pager.pager=p0 # $TESTTMP/sysrc:4
ui.editor=e1 # $TESTTMP/userrc:2
pager.pager=p2 # $PAGER
ui.editor=e1 # $TESTTMP/userrc:2