From: Junio C Hamano Date: Mon, 05 May 2025 21:14:39 GMT Subject: Re: [PATCH v2 03/10] t/unit-tests: convert reftable block test to use clar Message-ID: In-Reply-To: Patrick Steinhardt writes: > -M[], --find-renames[=] > Detect renames. If is specified, it is a threshold on the similarity index (i.e. amount > of addition/deletions compared to the file’s size). For example, -M90% means Git should > consider a delete/add pair to be a rename if more than 90% of the file hasn’t changed. > Without a % sign, the number is to be read as a fraction, with a decimal point before it. > I.e., -M5 becomes 0.5, and is thus the same as -M50%. Similarly, -M05 is the same as -M5%. > To limit detection to exact renames, use -M100%. The default similarity index is 50%. > > What you probably wanted to say is `--find-renames=90%`, but without the > percentage sign it is read as a fraction, where 1 means "exact copy" and > 0 means "all different". I am confused. -M without trailing %-sign is taken as fraction against 1 followed by the same number of '0' has the has digits. -M5 is 5 over 10, -M50 is 50 over 100. -M90 is 90 over 100, so -M90 and -M90% should mean the same thing. But you are right. When you want to claim your pre- and post- image files still correspond with each other in a meaningful way, even after making extensive change, you would want to _lower_, not raise, your similarity threshold. If the default is -M50, then -M90 would be a useful option to reject what Git (mistakenly) thinks are renames and tell it to instead consider they are removals and creations. THanks.