Fix Documentation for git-describe
Fix Documentation for git-describe

The documentation for git-describe says the default abbreviation is 8
hexadecimal digits while cache.c clearly shows DEFAULT_ABBREV set to 7.
This patch corrects the documentation.

Signed-off-by: Boyd Stephen Smith Jr <635280fd3f91cdbe1bc4d4ebceadc52af9df09bd@iguanasuicide.net>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git