checkout: use --aggressive when running a 3-way merge (-m).
checkout: use --aggressive when running a 3-way merge (-m).

After doing an in-index 3-way merge, we always do the stock
"merge-index merge-one-file" without doing anything fancy;
use of --aggressive helps performance quite a bit.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

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