Ævar Arnfjörð Bjarmason [off-list ref] writes:
We do not have such a pre-upload hook, but could have one. There's an
old thread from 2011 detailing some potential downsides:
https://public-inbox.org/git/CAMK1S_jaEWV=F6iHKZw_6u5ncDW0bPosNx-03W9bOLOfEEEY1Q@mail.gmail.com/
FWIW I think most servers who find themselves needing such a hook use it
to e.g. log how many fetches a given repository might serve, and end up
instead wrapping git commands in some custom shell.
Thanks for a concise summary.