UID switching was controlled via git-dameon's --user option in $daemon_flags.
This is problematic in case $gitdaemon_flags is unwittingly set to some value
which omits the --user option: git-daemon would then run as root.
The fix implemented here sets $daemon_user to _gitdaemon by default,
and leaves $daemon_flags empty by default. This ensures that git-daemon
runs as user _gitdaemon regardless of the value of $gitdaemon_flags.
Anyone using git-daemon should check their system. If gitdaemon is
currently running as root, set gitdaemon_user=_gitdaemon in rc.conf.local
and restart the service.
ok kn@
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