Hi, Let's say you have this a file with this content: ``` a b c d e f ``` Then you change it to this: ``` a b2 c d2 c e2 f ``` Note that most lines changed, but `c` remains unchanged but duplicated. Now `git diff --diff-algorithm=histogram` will show this diff: ``` diff --git a/file b/file index 0fdf397..7cfb042 100644 --- a/file +++ b/file @@ -1,6 +1,7 @@ a -b +b2 c -d -e +d2 +c +e2 f ``` I'm surprised the first "c" line is considered unchanged. I thought histogram diff was supposed to first match up unique lines between the two sides and then gradually try higher and higher counts if there were no unique lines. In this case, only "a" and "f" have count 1 (i.e. are unique) on both sides, so they would be matched up first. After that, "c" is unique on the left side but has a different count (namely 2) on the right side, so I would have thought that it should not be considered matching. Does anyone know if it's implemented this way on purpose? Actually, I think I remember reading that Git falls back to Myers in some cases, so maybe that's what's going on here? As some of you know, I work on the Jujutsu/jj VCS (https://github.com/jj-vcs/jj). We also use histogram diff (and only histogram diff) and actually allowed matching up lines with different counts a while ago, but I thought it seemed too arbitrary to line up the first matches if there were different counts, so we changed that. Then we got a report from a user that Git behaves differently. See https://github.com/jj-vcs/jj/issues/761#issuecomment-2581219294 for more details. Thanks
