git commit-tree

Alice/> git init
Initialized empty Git repository in /home/rene/github/github/git-internals/repos/commit-tree/Alice/.git/

Alice/> echo one > one.txt

Alice/> mkdir dir; echo two > dir/two.txt

Alice/> mkdir dir/subdir; echo three > dir/subdir/three.txt

Alice/> git update-index --add one.txt dir/two.txt dir/subdir/three.txt

Alice/> git write-tree
f572124f30244172618c7ba17d52a685174c4e0f

Alice/> git commit-tree f572124
022b79b088514af8b7ffce7cadea8abf3515d981