Bug#788525: git-remote-https segfault involving libgnutls

[ydirson at free.fr]

Package: libgnutls-deb0-28
Version: 3.3.15-5
Severity: grave
Justification: breaks other package

In my setup, a simple "git ls-remote https://github.com/irmen/Pyro4.git" (or any https repo
I had) would silently die, with only strace revealing git-remote-https segfaulting.

gdb shows:

Reading symbols from /usr/lib/git-core/git-remote-https...(no debugging symbols found)...done.
[New LWP 26284]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/i686/cmov/libthread_db.so.1".
Core was generated by `git-remote-https origin https://github.com/irmen/Pyro4.git'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0xb73e2788 in nettle_yarrow256_update () from /usr/lib/i386-linux-gnu/libnettle.so.4
(gdb) bt
#0  0xb73e2788 in nettle_yarrow256_update () from /usr/lib/i386-linux-gnu/libnettle.so.4
#1  0xb7356641 in do_device_source (init=<optimized out>, event=0xbfadc770, ctx=0xb73becc0 <rnd_ctx>) at rnd.c:147
#2  0xb7356804 in wrap_nettle_rnd_init (ctx=0xb73beedc <gnutls_rnd_ctx>) at rnd.c:241
#3  0xb72bf3e6 in _gnutls_rnd_init () at random.c:49
#4  0xb72b2d6d in gnutls_global_init () at gnutls_global.c:272
#5  0xb7293534 in lib_init () at gnutls_global.c:434
#6  0xb77d086e in call_init (l=<optimized out>, argc=argc at entry=3, argv=argv at entry=0xbfadc8e4, env=env at entry=0xbfadc8f4) at dl-init.c:78
#7  0xb77d0964 in call_init (env=0xbfadc8f4, argv=0xbfadc8e4, argc=3, l=<optimized out>) at dl-init.c:36
#8  _dl_init (main_map=0xb77e2930, argc=3, argv=0xbfadc8e4, env=0xbfadc8f4) at dl-init.c:126
#9  0xb77c2d3f in _dl_start_user () from /lib/ld-linux.so.2
(gdb) info threads
  Id   Target Id         Frame
* 1    Thread 0xb6e2c700 (LWP 26284) 0xb73e2788 in nettle_yarrow256_update () from /usr/lib/i386-linux-gnu/libnettle.so.4
(gdb) 

... and when I downgrade to 3.3.8-6+deb8u1 from stable, the segfault does away.
Anything to do with that nettle transition that should only affect unstable ?
My testing install doesn't seem to have any stuff from unstable related to that...