Subject: Re: [PATCH v2] checkout: eliminate unnecessary merge for trivial checkout

From: Junio C Hamano <[email-masked]>
Date: Mon, 12 Sep 2016 13:31:30 -0700

"Ben Peart" <[email-masked]> writes:

> I completely agree that optimizing within merge_working_tree would provide 
> more opportunities for optimization.  I can certainly move the test into
> that function as a first step.

Note that "optimizing more" was not the primary point of my
response.

Quite honestly, I'd rather see us speed up _ONLY_ obviously correct
and commonly used cases, while leaving most cases that _MAY_ turn
out to be optimizable (if we did careful analysis) unoptimized, and
instead have them handled by generic but known to be correct
codepath, if it means we do NOT to have to spend mental bandwidth to
analyze not-common case--that is a much better tradeoff.

The suggestion to move the check one level down in the callchain was
primarily to avoid the proposed optimization from being overly eager
and ending up skipping necessary parts of what merge_working_tree()
does (e.g. like I suspected in the review that the proposed patch
skips the check for "you have unmerged entries" situation).