In portage-2.1.8 there’s a new emerge –rebuilt-binaries option that is very useful for people who build binary packages and install them on multiple computers (using PORTAGE_BINHOST or shared PKGDIR). The option causes packages to be automatically reinstalled in cases when rebuilt binary packages are available (due to revdep-rebuild or similar cases). Rebuilds are detected by comparison of BUILD_TIME package metadata. This option is enabled automatically when using binary packages (–usepkgonly or –getbinpkgonly) together with –update and –deep.