Here is the latest of tor-git tor.install
post_install() {
  echo "==> "
  echo "==> Tor has been preconfigured to run as a client only"
  echo "==> Tor is experimental software, Do not rely on it for strong anonymity."
  echo "==> "
  post_upgrade
}

post_upgrade() {
  systemd-sysusers tor.conf
  systemd-tmpfiles --create tor.conf
  chown -R tor:tor /etc/tor
  chmod -R 750 /etc/tor
}

pre_remove() {
  echo
}
The previous edition had built fine but this one requires systemd
replace 
systemd-sysusers tor.conf
by 
applysys tor.conf
replace 
systemd-tmpfiles --create tor.conf
by 
/etc/s6/data/scripts/tmpfiles.sh --create --verbose
or 
pacopts applytmp
depending if you have pacopts installed or not
enjoy :)
6 days later
checking for SYSTEMD... no
configure: Okay, checking for systemd a different way...
checking for SYSTEMD... no
configure: error: Explicitly requested systemd support, but systemd not found
==> ERROR: A failure occurred in build().
    Aborting...
==> ERROR: Makepkg was unable to build tor-git.
PKGBUILD has this: 

    ./configure \
        --prefix=/usr --sysconfdir=/etc --localstatedir=/var \
        --enable-systemd --enable-zstd
        # --with-tcmalloc
        # --enable-openbsd-malloc

    make
}

check() {
    cd "$srcdir/tor"
    make test || true
}

package() {
    cd "$srcdir/tor"
    make DESTDIR="$pkgdir" install

    rm -f "$pkgdir/etc/tor/tor-tsocks.conf"
    install -Dm640 "$srcdir/torrc"        "$pkgdir/etc/tor/torrc"
    install -Dm644 "$srcdir/tor.service"  "$pkgdir/usr/lib/systemd/system/tor.service"
    install -Dm644 "$srcdir/tor.tmpfiles" "$pkgdir/usr/lib/tmpfiles.d/tor.conf"
    install -Dm644 "$srcdir/tor.sysusers" "$pkgdir/usr/lib/sysusers.d/tor.conf"
I took a wild shot and deleted those two lines with systemd in it, on $pkgdir/usr/lib/systemd/system I did $pkgdir/usr/lib/system
and it seems to have worked
replace the configure option --enable-systemd by --disable-systemd, remove the line install -Dm644 "$srcdir/tor.service" "$pkgdir/usr/lib/systemd/system/tor.service" but do not remove install -Dm644 "$srcdir/tor.tmpfiles" "$pkgdir/usr/lib/tmpfiles.d/tor.conf" install -Dm644 "$srcdir/tor.sysusers" "$pkgdir/usr/lib/sysusers.d/tor.conf", we have a wrapper for this kind of stuff
2 years later
The above was in reference to an AUR package that was called tor-git but the current one is abandoned and points to a dead git link.

The correct way to install tor is to trust torproject directly.
https://www.torproject.org/download/tor/
This has no systemd dependency. It is just pure tor as it comes from the source.
https://www.torproject.org/download for the browser which includes tor

There is also alpha links for the next generation tor which for the past decade haven't had any problems.
Make sure you download the sig file and test the archive before you use it.

You uncompress and extract the archive in /tmp or some place safe, you cd into tor.3...xxx run the configure file then make install as root.

You should also learn to configure /etc/torrc and study how to run this safely. I create a special user, nologin, no groups, and run tor as daemon with that user who has no wheel or other rights to the system. You use it, and then exit.

It is not a good idea to leave tor running when it is not directly in use. Tor emphasizes to learn to use it correctly otherwise you might as well not use it at all. So if you run it as a 66 service it is better you make a tree for it and enable/disable the tree separately from other services that run all the time.

It is also good practice to visit often the site and be alert of new versions, it is most often very crucial you update immidiately and not use an older version of tor. Don't expect arch or obarun to do this for you.

My 2c

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