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

Calculating dependencies ... done!
Dependency resolution took 0.96 s (backtrack: 0/20).

[ebuild  N     ] mail-client/thunderbird-l10n-158.0:0/stable::gentoo  L10N="-af -ar -ast -be -bg -br -ca -cak -cs -cy -da -de -dsb -el -en-CA -en-GB -es-AR -es-ES -et -eu -fi -fr -fy -ga -gd -gl -he -hr -hsb -hu -id -is -it -ja -ka -kab -kk -ko -lt -lv -ms -nb -nl -nn -pa -pl -pt-BR -pt-PT -rm -ro -ru -sk -sl -sq -sr -sv -th -tr -uk -uz -vi -zh-CN -zh-TW" 0 KiB

Total: 1 package (1 new), Size of downloads: 0 KiB