How do such a tiny repo cause git to run out of memory? The secret is that git de-duplicates “blobs” (which are used to store files) to make repositories smaller and allow using the same blob when a file remains unchanged between commits. Git also allows de-duplication of “tree” objects (which define the directory structure in a repository). git-bomb tries to make a billion files, however it only has 10 references to the file blob and only has 10 tree objects in all.

source: L