On Mon, Mar 8, 2021 at 4:10 PM Elijah Newren via GitGitGadget <gitgitgadget@xxxxxxxxx> wrote: > > This series depends textually on ort-perf-batch-8, but semantically it's > almost completely unrelated and can be reviewed without any familiarity with > any of the previous patch series. > > There are no changes since v1; it's just a resend just over a week later to > bump it so it isn't lost. > > === Basic Optimization idea === > > This series determines paths which meet special cases where detection of > renames is irrelevant, where the irrelevance is due to the fact that the > merge machinery will arrive at the same result regardless of whether a > rename is detected for any of those paths. This series represents > "Optimization #2" from my Git Merge 2020 talk[1], though this series has > some improvements on the optimization relative to what I had at that time. > > The basic idea here is: > > We only need expensive rename detection on the subset of files changed on > both sides of history (for the most part). I know this series was already reviewed and even a subsequent series was reviewed, but I thought I'd insert a bit of history trivia: I first submitted this optimization in late 2017 as an RFC at https://lore.kernel.org/git/20171110222156.23221-9-newren@xxxxxxxxx/. Unfortunately I had only handled the "for the most part" piece, not the other special cases. I knew not handling those other cases caused bugs, but didn't readily find a solution for them at the time. I kept mulling it over periodically despite being switched onto other projects; eventually I weaseled my way into being able to work on it again and with some effort was able to work out the other necessary conditions and audit the code to verify I had all the cases covered. Those "other cases" were much more easily expressed in the context of merge-ort's data structures than merge-recursive's, in part because merge-ort's data structures were picked to help me solve this optimization problem and the various known failing testcases that I wanted to fix.
