Jakub Narebski <jnareb@xxxxxxxxx> writes: > ... > and if it detects that the file "file0" is completely rewritten, > it changes it to: > > ------------------------------------------------ > :100644 000000 bcd1234... 0000000... D file0 > :000000 100644 0000000... 0123456... A file0 > ------------------------------------------------ > > Shouldn't the last block read for the modern git read: > > ------------------------------------------------ > :100644 000000 bcd1234... 0123456... M99 file0 > ------------------------------------------------ Correct. The description is based on an earlier round of the code before 366175ef8c3b1e145f4ba846e63a1dea3ec3cacc (Rework -B output). "git show" of that patch has description in its changes to Documentation/diffcore.txt. The original motivation of -B was not about helping three way renames it allows you when used with -M/-C. It was about showing textual diff more readably for quite dissimilar filepairs. > Third: Do "git diff --no-index" (filesystem diff) can show breaking / > use dissimilarity? I couldn't make it work... It doesn't, for two reasons. * Look at diffcore_break(). It breaks filepairs with identical paths and nothing else. The reason for this check is that the caller can call diffcore_rename() _before_ diffcore_break() [*1*] and a filepair that was detected as renamed pair ought to be already found similar enough. These days, I think you can replace the check with p->renamed_pair. * Look at diffcore_merge_broken(), which is responsible for re-merging a broken pair. Because we match them by looking at their names (iow, we do not use pointers to link halves of a broken pair pointing at each other). This was correct before "no-index" stuff because "git diff" was about comparing pairs of blobs found at corresponding paths in two tree-like things (i.e. "a/one" and "b/one" corresponds to each other when you do "git diff -- one"). The modification to introduce no-index forgot to update this logic. If you wanted to fix this, you can change p->broken_pair from a boolean to a pointer that points at the other half of the broken pair (and record that when we break a pair in diffcore_break()), and look at that pointer to decide which one to match up with which other one in diffcore_merge_broken(). Together with a change to look at p->renamed_pair instead of paths I mentioned, I think it would work more like the regular git diff for "no-index" case. I consider that "no-index" frontend more or less a bolted on half-baked hack that covers only minimally necessary cases to serve as non-git "diff" replacement, without sharing enough with the real "git diff" internals; I would not be surprised at all if there are more corner cases like this that does not work. But I do not think it is fundamentally unfixable. The change to add "no-index" support just needed to be more careful, and it is not too late to make it so. [Footnote] *1* diffcore was designed as a generic library to allow experimenting more combinations of transformations than what then-current git used. All of our existing callers ended up calling the transformations in the same order (i.e. the order diffcore_std() calls them), but individual transformations were written not to assume too much about the order they would be called. - To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
