On Wed, Feb 15, 2023 at 02:44:59PM +0000, Phillip Wood wrote: > Indeed. Ironically as there are no unique context lines in that example the > blank lines are being matched by patience implementation falling back to the > myers algorithm. Normally the myers implementation tries to avoid matching > common context lines between two blocks of changed lines but I think because > in this case it is only called on a small part of the file the blank lines > are not common enough to trigger that heuristic. I've got a patch[1] that > stops the patience implementation falling back to the myers algorithm and > just trims any leading and trailing context. On the whole it I think it > gives more readable diffs but I've not got any systematic data to back that > up. I also suspect there are pathological cases such as each line in the > file being duplicated where the falling back to the myers algorithm gives a > much better result. Ah, I should have suspected it was something like that (since one of the purposes of patience is trying not to key on meaningless lines). I tried your patch on my test case, and the result is even more readable than the myers output, because it really was effectively a complete rewrite of the function. It is, of course, not the minimal diff. I'm not sure if there would be cases where you'd prefer the minimal. I guess if each stanza's change really was independent of the others. But if there is no commonality except for blank lines, I find it hard to imagine that it's much worse to just treat the whole thing as a block. Anyway, thank you (and Elijah) for explaining. I'm getting more comfortable with the idea of switching the default. -Peff
