t3702-add-edit.sh failure in next

I'm seeing a reproducible failure in t3702 on AIX 5.3, shell set to
bash (v2.05b)

The 'test_cmp orig-patch expected-patch' is seeing this diff:

2c2
< index b9834b5..52aff4c 100644
---

index b9834b5..0b8f197 100644

The index seems to contain the expected content.

I've tried to eliminate GIT* environment variables which might be
affecting the commit id, and tried adding extra test_ticks, but I'm
afraid I can't work out what's up here.

Normally all tests pass fine with the exception of some skipped
because of known iconv issues on this platform.

Mike