Re: [PATCH 3/3] diff: correct warning message when renameLimit exceeded

On Tue, Jul 13, 2021 at 6:10 PM Junio C Hamano [off-list ref] wrote:

Elijah Newren [off-list ref] writes:

quoted

The exhaustiveness of the quadratic portion comes from comparing each
file to more other files, not in using a different type of comparison.

Exactly.  By culling potential matches early with heuristics, we
make a trade-off of risking false-negatives but save a lot of cycles
while trying to find "renames with modifications (which is what we
called 'inexact rename')", and my comment equated  fewer false-negatives
with more precision.

Okay, I think I'm following what you're saying now, mostly, but I'm
curious about the false negative comment.

Am I mixing up negatives/positives (as I'm prone to do), or would it
be more correct to say the new algorithm risks suboptimal positives
rather than that it risks false negatives?

In particular, the new algorithm will compare files with the same
basename and just accept that pairing if they are similar enough, even
if there might be a better match elsewhere.  However, a lack of a
match in same-basenamed files will not cause those files to have no
match; they will instead just be included in the exhaustive detection
portion, so we can still detect renames for such paths.