We exclude .git/hooks from symlinking into the temporary working tree,
which avoids the commit hook being run for the temporary branch anyway.
This avoids the wiki not being updated if an orthogonal change is
received in process A, while process B prepares a revert that is
subsequently cancelled.
(cherry picked from commit
d092b0b77701a4c5cd9c8464b774a6a1da1f02cd)