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

Calculating dependencies ... done!
Dependency resolution took 0.99 s (backtrack: 0/20).

[ebuild  N     ] app-vim/nerdtree-7.1.3-r1::gentoo  163 KiB
[ebuild  N     ] app-vim/nerdtree-tabs-1.4.7-r1::gentoo  11 KiB

Total: 2 packages (2 new), Size of downloads: 174 KiB