Svnimport problem for openwrt repo

Just tried today to sync my openwrt copy, but it seems that their extensive 
use of svn makes git-svnimport fail.
In particular, around commit #5089, I get the attached error (having printed 
the 'system' line). That commit should be the one when they merged 
their 'buildroot-ng' branch into the trunk (major changes, that is).
I have little to no time to debug the issue. Would you please give me a clue 
how to solve the issue and keep on using git-svnimport? Of course, I could 
even let you clone my repo or even work on it..
Hint: is there something wrong in the git-update-index arguments  I have 
there?