Here used to be hosted:
A test repository I got from David Turner (at the time at Twitter)
which somewhat emulates the size & shape of the Twitter monorepo
But in late 2019 GitHub support (very reasonably, I might add) asked me to put out this particular dumster fire on their infrastructure, it had blown up to 650 GB in on-disk size!
For me this repo is ~3.5G of .git, but is pathological in lots of other ways. Maybe why it grew so much will be discussed on-list, maybe not.
For now a copy of this can still be found at https://gitlab.com/avar/2015-04-03-1M-git or at least until GitLab also asks me to delete it, but perhaps they have different repack settings that don't make it so pathological.