subrepo: do not push mercurial subrepos whose store is clean This patch stops mercurial from pushing unmodified subrepos. An unmodified subrepo is one whose store is "clean" versus a given target subrepo. Note that subrepos may have a clean store versus a target repo but not versus another. This patch handles this scenario by individually keeping track of the state of the store versus all push targets. Tests will be added on the following revision.