Merge branch 'ps/abbrev-length-before-setup-fix'

Setting core.abbrev too early before the repository set-up
(typically in "git clone") caused segfault, which as been
corrected.

* ps/abbrev-length-before-setup-fix:
  object-name: don't try to abbreviate to lengths greater than hexsz
  parse-options-cb: stop clamping "--abbrev=" to hash length
  config: fix segfault when parsing "core.abbrev" without repo

diff --cc config.c
Simple merge