* Clean-up HookPreReceive and restore functionality for pushing non-standard refs
There was an inadvertent breaking change in #15629 meaning that notes refs and other
git extension refs will be automatically rejected.
Further following #14295 and #15629 the pre-recieve hook code is untenably long and
too complex.
This PR refactors the hook code and removes the incorrect forced rejection of
non-standard refs.
Fix #16688
Signed-off-by: Andrew Thornton <art27@cantab.net>
