On Tue, Apr 02, 2013 at 02:15:17PM -0700, Junio C Hamano wrote: > John Keeping <j...@keeping.me.uk> writes: > > > When the source file is empty, the calculation of the merge score > > results in a division by zero. Since the merge score is initialized to > > zero, it makes sense to just leave it as it is if the source size is > > zero. This means that we still use the extent of damage metric to > > decide whether to break the filepair. > > Well spotted. An empty blob to another blob that is larger than 400 > bytes will trigger div0, and it makes sense to leave merge-score to > 0 (i.e. do not show as whole-delete-then-whole-add after rename > detection is done and the broken filepair is merged back). > > Actually, if src->size is 0, we probably shouldn't break the filepair > in the first place. That is, if your preimage and postimage looked > like these: > > > == preimage == == postimage == > > F (empty file) F (a large file) > E (a new empty file) > > do we want to see F renamed to E and then a new file created as F > while running "git diff -B -M"? I doubt it. > > So in that sense, this might be a better solution. I dunno.
I considered this, but didn't quite understand the code well enough to be sure that was the right thing to do. Does it make sense to bail out early if dst->size is zero as well? The message for commit 6dd4b66 (Fix diffcore-break total breakage) indicates that "don't bother to break small files" is wrong in some cases, but it I wonder if "don't bother to break empty files" is okay. > diffcore-break.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/diffcore-break.c b/diffcore-break.c > index 44f8678..eabafd5 100644 > --- a/diffcore-break.c > +++ b/diffcore-break.c > @@ -67,6 +67,8 @@ static int should_break(struct diff_filespec *src, > max_size = ((src->size > dst->size) ? src->size : dst->size); > if (max_size < MINIMUM_BREAK_SIZE) > return 0; /* we do not break too small filepair */ > + if (src->size == 0) > + return 0; /* we do not let empty files get renamed */ > > if (diffcore_count_changes(src, dst, > &src->cnt_data, &dst->cnt_data, -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
