contrib/completion: --line-number to git grep
contrib/completion: --line-number to git grep

The "-n" option of "git grep" gained a synonym "--line-number" with
commit 7d6cb10b ("grep: Add the option '--line-number'", 2011-03-28).

Teach bash-completion about it.

Signed-off-by: Michał Kiedrowicz <3303283adeb04caefcc13da64be4ce1c6c137c62@gmail.com>
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