if I export myself LC_ALL=C it just works.
don't know why it was failing from the patches you have provided me

tested with both applied and still fails with LC_ALL=fr_FR.UTF8

nope this one does not work:

I can confirm it fixes it, thank you very much!

So I'm using svn 1.8.9 and I can reproduce on every svn 1.8 version (I haven't tried earlier version)
arc diff --only is giving this result: https://phabric.freebsd.org/differential/diff/651/ which is broken
with --trace I got the following:

What can I provide more to help diagnose this, or I could probably fix it myself if one can give me a direction where to look in the code?

the file devel/pkg-gmake/Makefile is wrong
if you have a look you see it appears twice (the numbering of line restart to 1 after line 29)