merge: small code readability improvement

After our loop through the selected strategies, we compare best_strategy to wt_strategy. This is fine, but the fact that the code setting best_strategy sets it to use_strategies[i]->name requires a little bit of extra checking to determine that at the time of setting, that's the same as wt_strategy. Just setting best_strategy to wt_strategy makes it a little easier to verify what the loop is doing, at least for this reader. Further, use_strategies[i]->name is used in a number of places, where we could just use wt_strategy. The latter takes less time for this reader to parse (one variable name instead of three), so just use wt_strategy to make the code slightly faster for human readers to parse. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>