You can build it in a chroot or VM which you completely trash afterwards.

Did the "or" part...

There are problems in the `release` files...

(yeti@kumari:13)/wrk/mirrors$ ./devuan.sh 
Mirroring to /wrk/mirrors/devuan from http://auto.mirror.devuan.org/merged/
Arches: arm64
Dists: ascii,ascii-backports,ascii-security
Sections: main,contrib,non-free
Pdiff mode: use
Not checking Release gpg signatures.
Will clean up after mirroring.
Attempting to get lock ...
Updating remote trace files (using rsync) ...
rsync: failed to connect to auto.mirror.devuan.org (2001:41d0:8:2c55::a2): Connection refused (111)
rsync: failed to connect to auto.mirror.devuan.org (46.105.191.77): Connection refused (111)
rsync error: error in socket IO (code 10) at clientserver.c(128) [Receiver=3.1.1]
Warning: failed to use rsync to download extra files.
Getting meta files ...
[  0%] Getting: dists/ascii/Release...   #** GET http://auto.mirror.devuan.org/merged/dists/ascii/Release ==> 200 OK
ok
[  0%] Getting: dists/ascii/Release.gpg...       #** GET http://auto.mirror.devuan.org/merged/dists/ascii/Release.gpg ==> 200 OK
ok
[  0%] Getting: dists/ascii-backports/Release...         #** GET http://auto.mirror.devuan.org/merged/dists/ascii-backports/Release ==> 200 OK
ok
[  0%] Getting: dists/ascii-backports/Release.gpg...     #** GET http://auto.mirror.devuan.org/merged/dists/ascii-backports/Release.gpg ==> 200 OK (1s)
ok
Duplicate dist ascii.
WARNING: releasing 1 pending lock...

`http://ftp.debian.org/debian/dists/stretch-backports/Release`:

Origin: Debian Backports
Label: Debian Backports
Suite: stretch-backports
Codename: stretch-backports
Date: Wed, 26 Jul 2017 02:29:47 UTC
Valid-Until: Wed, 02 Aug 2017 02:29:47 UTC
NotAutomatic: yes
ButAutomaticUpgrades: yes
Acquire-By-Hash: yes
Architectures: amd64 arm64 armel armhf i386 mips mips64el mipsel ppc64el s390x
Components: main contrib non-free
Description: Backports for the Stretch distribution
MD5Sum:
 d41d8cd98f00b204e9800998ecf8427e        0 contrib/Contents-amd64

`http://auto.mirror.devuan.org/merged/dists/ascii-backports/Release`:

Origin: Devuan
Label: ascii-backports
Suite: ascii-backports
Version: 2.0.0
Codename: ascii
Date: Tue, 25 Jul 2017 20:31:36 UTC
Valid-Until: Tue, 01 Aug 2017 20:31:36 UTC
NotAutomatic: yes
ButAutomaticUpgrades: yes
Architectures: alpha amd64 arm64 armel armhf hppa i386 ia64 mips mipsel powerpc ppc64el s390x sparc
Components: main contrib non-freeMD5Sum:
  8a4b59cb71d78f27c2cd19431cccd2f8      808 non-free/binary-amd64/Packages.xz

There's a linefeed missing between `non-free` and `MD5Sum:` and the field `Codename:` probably should be `ascii-backports` (same for `ascii-proposed-updates` and `ascii-updates`).

Apart from these showstoppers for mirroring `ascii-backports`, `ascii-proposed-updates` and `ascii-updates` the remaining results look ok so far:

(yeti@kumari:13)/wrk/mirrors$ du -sh devuan/*/*
16M     devuan/dists/ascii
180K    devuan/dists/ascii-security
0       devuan/dists/testing
0       devuan/dists/testing-security
56G     devuan/pool/DEBIAN
20M     devuan/pool/DEVUAN
8,0K    devuan/project/trace

Currently I have no ASCII/arm64⁽¹⁾ system, so I cannot test installing from this mirror.

(1): Last weekend I reinstalled all my Devuan-PIs with Jessie because...
...eeeehhh... ***cough³*** <whisper> ASCII </whisper>

——————————

Edit@20170726-1042-UTC: Bonus question.

What's the difference between `auto.mirror.devuan.org` and `packages.devuan.org`?

——————————

Edit@20170726-1054-UTC: Jessie has the same `Codename:` problems.

E.g.: .../jessie-proposed-updates/Release

Show the error.

If you know enough, you can ... sure ... but then you definitely do know why not to build an own distribution too... :-P

I'm on Debian since the mid90s and up to Debian6 it was near to boringly smooth... ;-) ...so I had the time to play with other stuff too. Then Wheezy made things worse and Jessie got a bit better again, but nothing beats my time with Debian6... even Evolution was stable those days! ***sigh!***

I tried Ubuntu when it was very young and morphing a Debian to Ubuntu was like a version upgrade (luckily it worked back to Debian the same way too :-P). Later, when I got my 1st notebook and I was told Ubuntu would  work better with "such modern stuff", I tried it again. Those were 6hrs of torture and then the notebook got Lenny (was "testing" at that time) and all was good again.

I think Ubuntu's small differences to Debian were worse for me than having a totally different pet (like BSD) under my fingers...

And now here we are... and systemd has to stay outside... \o/

The same here...

I choose the freedom not to throw away my computers which need bad blobs.

Come on... Midory still wants to start an external App for ftp://.
That's crazy!
I don't even dare to try gopher://.

(This version of) Midori definitely will not be my furure browser.

As soon as NetBSD is using APT!

\o/   Now that makes a perfect Towel Day!   \o/

Current X11 with all those mean extensions is not as network transparent as it used to be a decade ago.
:-(

Sure it kind of works today but more and more programs are using features that put a horrible amount of data in motion or are not network transparent at all.

There was a video of Wayland makers ((ex-)X11 coders) declaring X11 dead because of it's ugly add-ons over the decades. But who has made them if not the X11 coders?

Now that's taken as reason for Wayland...

X11 may be dead but it was killed by its own maintainers!

Not amused at all I am!

I loved XDMCP!

*sigh!*