On Fri, Aug 07, 2020 at 06:26:30PM -0400, Jeff King wrote:
> On Fri, Aug 07, 2020 at 03:05:27PM -0700, Junio C Hamano wrote:
>
> > Jeff King <peff@xxxxxxxx> writes:
> >
> > > Dropping it entirely, as below, doesn't break any tests. Junio, do you
> > > know of a case this is meant to improve?
> >
> > I think the only conceivable case is that in the middle of a single
> > block of text in an ancient version, another block of lines gets
> > inserted during the evolution of the file, but in the end these
> > intermediate edits all go away and the same original text remains.
> >
> > In such a case, without coalescing, we would not treat the original
> > single block of text as a single unit.
>
> Yeah, that makes sense, and it should be possible to construct a case
> based on that.
It was even easier than I expected. :)
Try this:
git init repo
cd repo
seq 20 >file
git add file
git commit -m base
{ seq 10; echo foo; seq 11 20; } >file
git commit -am cruft
seq 20 >file
git commit -am revert
git blame --root --porcelain file
With the coalescing, we get a single 20-line block:
25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 1 1 20
author Jeff King
...
1
...
25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 11 11
11
and without it, we get two 10-line blocks:
25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 1 1 10
author Jeff King
...
1
...
25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 11 11 10
11
I doubt it really matters all that much in practice, but it's possible
some consumer of --porcelain relies on us giving minimal blocks.
So that argues for fixing blame_coalesce() to make sure that we coalesce
only when the blocks are adjacent in both the source and the result.
Otherwise we're losing information.
-Peff
