completion: Add --full-diff to log options

Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: tmzullinger

contrib/completion/git-completion.bash

@@ -1165,7 +1165,7 @@ _git_log ()
 			$__git_log_shortlog_options
 			$__git_log_gitk_options
 			--root --topo-order --date-order --reverse
-			--follow
+			--follow --full-diff
 			--abbrev-commit --abbrev=
 			--relative-date --date=
 			--pretty= --format= --oneline