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

Calculating dependencies ... done!
Dependency resolution took 1.03 s (backtrack: 0/20).

[ebuild  N     ] dev-libs/jemalloc-5.4.0-r2:0/2::gentoo  USE="stats -debug -lazy-lock -prof -xmalloc" 893 KiB
[ebuild  N     ] dev-util/difftastic-0.71.0::gentoo  USE="-debug" 35046 KiB

Total: 2 packages (2 new), Size of downloads: 35938 KiB