// 
#emerge -aDNuv --keep-going @world

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild r U #] app-text/poppler-9999:0/9999::gnome-kit [0.52.0:0/66::gnome-kit] USE="cairo cxx introspection jpeg jpeg2k lcms png qt5 tiff utils -cairo-qt% -cjk -curl -debug -doc -nss -qt4" 0 KiB
[ebuild U ] net-libs/webkit-gtk-2.18.5:4/37::gnome-kit [2.18.4:4/37::gnome-kit] USE="(X) egl geolocation gnome-keyring gstreamer introspection jit libnotify nsplugin opengl webgl (-aqua) -coverage -doc -gles2 -spell {-test} -wayland" 0 KiB
[ebuild rR ] net-print/cups-filters-1.19.0::net-kit USE="dbus foomatic jpeg pdf png postscript tiff -ipp_autosetup -ldap -pclm -perl -static-libs {-test} -zeroconf" 0 KiB
[ebuild rR ] app-misc/pdfpc-4.0.8::nokit USE="gstreamer" 0 KiB
[ebuild rR ] sci-libs/gdal-2.2.3-r1:0/2.2::science-kit USE="aux_xml geos gif jpeg jpeg2k pdf png python webp -armadillo -curl -debug -doc -fits -gml -hdf5 -java -mdb -mysql -netcdf -odbc -ogdi -opencl -oracle -perl -postgres -spatialite -sqlite -threads -xls" PYTHON_TARGETS="python2_7 python3_4 -python3_5 -python3_6" 0 KiB
[ebuild U ] app-text/texlive-core-2017-r3::text-kit [2017-r2::text-kit] USE="X luajittex -cjk -doc -source -tk -xetex" 0 KiB
[ebuild rR ] app-office/scribus-1.5.3::desktop-kit USE="boost minimal pdf -debug -examples -graphicsmagick -hunspell -osg -scripts -templates -tk" LINGUAS="fr -af -ar -bg -br -ca -ca_ES -cs -cs_CZ -cy -cy_GB -da -da_DK -de -de@1901 -de_CH -de_DE -el -en_AU -en_GB -en_US -eo -es -es_ES -et -eu -fa_IR -fi -fi_FI -gl -he -he_IL -hr -hu -hu_HU -ia -id -id_ID -is -is_IS -it -ja -kab -kn_IN -ko -ku -la -lt -lt_LT -nb_NO -nl -nn_NO -pl -pl_PL -pt -pt_BR -pt_PT -ro -ro_RO -ru -ru_RU -sa -sk -sk_SK -sl -sl_SI -so -sq -sr -sv -sv_SE -te -th_TH -tr -uk -uk_UA -zh_CN -zh_TW" PYTHON_TARGETS="python2_7" 0 KiB
[ebuild U ] app-emulation/virtualbox-5.2.6::nokit [5.2.4::nokit] USE="alsa opengl pam pulseaudio python qt5 sdk udev -debug -doc -headless -java -libressl -lvm -pax_kernel -vboxwebsrv -vnc" PYTHON_TARGETS="python2_7" 0 KiB
[ebuild U ] www-client/firefox-57.0.4::net-kit [57.0::net-kit] USE="dbus gmp-autoupdate nsplugin pulseaudio screenshot -bindist -custom-cflags -custom-optimization -debug -eme-free -hardened -hwaccel -jack (-neon) -pgo (-selinux) -startup-notification -system-harfbuzz (-system-icu) -system-jpeg -system-libevent -system-libvpx (-system-sqlite) {-test} -wifi" L10N="fr -ach -af -an -ar -as -ast -az -bg -bn-BD -bn-IN -br -bs -ca -cak -cs -cy -da -de -dsb -el -en-GB -en-ZA -eo -es-AR -es-CL -es-ES -es-MX -et -eu -fa -ff -fi -fy -ga -gd -gl -gn -gu -he -hi -hr -hsb -hu -hy -id -is -it -ja -ka -kab -kk -km -kn -ko -lij -lt -lv -mai -mk -ml -mr -ms -nb -nl -nn -or -pa -pl -pt-BR -pt-PT -rm -ro -ru -si -sk -sl -son -sq -sr -sv -ta -te -th -tr -uk -uz -vi -xh -zh-CN -zh-TW" 0 KiB
[ebuild U ] app-emulation/virtualbox-extpack-oracle-5.2.6.120293::nokit [5.2.4.119785::nokit] 0 KiB
[ebuild U ] mail-client/thunderbird-52.5.2::net-kit [52.4.0::net-kit] USE="crypt dbus jemalloc minimal pulseaudio -bindist -custom-cflags -custom-optimization -debug -gtk2 -hardened -ldap -lightning -mozdom (-neon) (-rust) (-selinux) -startup-notification (-system-cairo) -system-harfbuzz -system-icu -system-jpeg -system-libevent -system-libvpx -system-sqlite -wifi" L10N="fr -ar -ast -be -bg -bn-BD -br -ca -cs -cy -da -de -el -en-GB -es-AR -es-ES -et -eu -fi -fy -ga -gd -gl -he -hr -hsb -hu -hy -id -is -it -ja -ko -lt -nb -nl -nn -pa -pl -pt-BR -pt-PT -rm -ro -ru -si -sk -sl -sq -sr -sv -ta-LK -tr -uk -vi -zh-CN -zh-TW" 0 KiB
[ebuild rR ] app-text/atril-1.18.0::text-kit USE="caja dbus gnome-keyring introspection postscript tiff -debug -djvu -dvi -epub -t1lib -xps" 0 KiB
[ebuild rR ] app-office/libreoffice-5.4.2.2::kde-kit USE="branding cups dbus eds gnome gstreamer gtk gtk3 pdfimport -bluetooth -coinmp -collada -debug -firebird -gltf -googledrive -java -jemalloc -kde -libressl -mysql -odk -postgres -quickstarter {-test} -vlc" LIBREOFFICE_EXTENSIONS="-nlpsolver -scripting-beanshell -scripting-javascript -wiki-publisher" PYTHON_SINGLE_TARGET="python3_4 -python2_7 -python3_5 -python3_6" PYTHON_TARGETS="python2_7 python3_4 -python3_5 -python3_6" 0 KiB
[ebuild rR ] app-misc/tracker-1.8.0:0/100::gnome-kit USE="exif flac gif gstreamer gtk iso jpeg miner-fs mp3 nautilus networkmanager pdf tiff vorbis xml -cue -ffmpeg -firefox-bookmarks -gsf -iptc (-libav) -playlist -rss -stemmer {-test} -thunderbird -upnp-av -upower -xmp -xps" 0 KiB
[ebuild rR ] app-text/evince-3.20.1-r1:0/evd3.4-evv3.3::gnome-kit USE="gnome gnome-keyring gstreamer introspection nautilus nsplugin postscript tiff -djvu -dvi -t1lib -xps" 0 KiB
[ebuild U ] gnome-extra/nm-applet-1.8.6::gnome-kit [1.4.6-r1::gnome-kit] USE="introspection modemmanager -gcr% (-selinux) -teamd" 0 KiB

Total: 16 packages (8 upgrades, 8 reinstalls), Size of downloads: 0 KiB

The following packages are causing rebuilds:

app-text/poppler-9999:0/9999::gnome-kit, ebuild scheduled for merge causes rebuilds for:
app-misc/tracker-1.8.0:0/100::gnome-kit, ebuild scheduled for merge
app-misc/pdfpc-4.0.8:0/0::nokit, ebuild scheduled for merge
app-text/evince-3.20.1-r1:0/evd3.4-evv3.3::gnome-kit, ebuild scheduled for merge
app-office/libreoffice-5.4.2.2:0/0::kde-kit, ebuild scheduled for merge
sci-libs/gdal-2.2.3-r1:0/2.2::science-kit, ebuild scheduled for merge
net-print/cups-filters-1.19.0:0/0::net-kit, ebuild scheduled for merge
app-office/scribus-1.5.3:0/0::desktop-kit, ebuild scheduled for merge
app-text/atril-1.18.0:0/0::text-kit, ebuild scheduled for merge
app-text/texlive-core-2017-r3:0/0::text-kit, ebuild scheduled for merge


Would you like to merge these packages? [Yes/No] y