Re: [PATCH] git-add--interactive: Preserve diff heading when splitting hunks

Jeff King [off-list ref] writes:

One, there is a slightly funny artifact in that the hunk header comes
from the top of the context line, and that top is a different position
for each of the split hunks. So in a file like:

  header_A
      content
  header_B
      one
      two
      three
      four

you might have a diff like:

  @@ ... @@ header_A
   header_B
       one
       two
  +    new line 1
       three
  +    new line 2
       four

The hunk header for "new line 1" is "A", because "B" itself is part of
the context. But the hunk header for "new line 2", if it were an
independent hunk, would be "B". We print "A" because we copy it from the
original hunk.

It probably won't matter much in practice (and I can even see an
argument that "A" is the "right" answer).

I tend to agree with both points.

And figuring out "B" here
would be prohibitively difficult, I would think, as it would require
applying the funcname rules internal to git-diff to a hunk that git-diff
itself never actually sees.

You can actually apply a split hunk being proposed to a temporary
file and then ask "git diff" about it, so I do not think difficult
is too much of an issue, but I doubt we would want to see header_B,
exactly because when the user says "Split this hunk", s/he is very
well aware that the second one is artificial and was split from the
original hunk whose header said header_A.

Since the output from your patch is strictly better than what we saw
before, I think there is no reason we cannot leave such an improvement
to later (or never).

Yes.

On Mon, May 12, 2014 at 02:07:15PM -0700, Junio C Hamano wrote:

quoted

And figuring out "B" here
would be prohibitively difficult, I would think, as it would require
applying the funcname rules internal to git-diff to a hunk that git-diff
itself never actually sees.

You can actually apply a split hunk being proposed to a temporary
file and then ask "git diff" about it, so I do not think difficult
is too much of an issue,

True, I didn't think of that.

but I doubt we would want to see header_B,
exactly because when the user says "Split this hunk", s/he is very
well aware that the second one is artificial and was split from the
original hunk whose header said header_A.

Right, that's along the lines of the "you could make the argument" I was
thinking of. Since you are thinking it, too, I'm definitely in favor of
stopping at Ævar's patch and seeing if anybody even notices or
complains.

Thanks.

-Peff