The second file is just not stored, because git thinks it's already there. Nothing complicated there.

Discussed here: https://stackoverflow.com/questions/9392365/how-would-git-ha...

It costed 6500 CPU years to create the first collision containing a valid pdf document. Storing both versions into git still works, because git prepends a header before creating the SHA-1 of the blob. I believe because of that it is harder to create a git blob collision than a pdf collision. (I admit I did neither read very carefully nor try to think it through very seriously.)

On the other hand, if you are still running subversion, you pretty much lose the repo in this case: https://arstechnica.com/information-technology/2017/02/water...