compactionHeuristic=true is not used by interactive staging

> Hello,
> I just did a fresh clone of git from Github and installed the version
> 2.9.0 on Fedora 22.
> 
> I tried the new compactionHeuristic = true, which is awesome.
> The only thing that struck me was that this option was not used when
> doing an interactive staging, meaning `git diff` and `git add -p` will
> format patches differently. Perhaps this is intended and there is a
> way to force interactive staging to use specific diff options, but I
> did not find it in the doc.

> Jeff King <peff@peff.net> writes:
>
>> Nobody noticed so far because originally the compaction heuristic was on
>> by default, and so just worked everywhere. But we backed off on that at
>> the last minute after finding a few cases where the diff looks worse.
>
> Yup, and that is why this is called "experimental" in the release
> notes ;-)

> On Wed, Jun 15, 2016 at 08:24:47AM +0200, Alex Prengère wrote:
>
>> I see, it makes sense ;-) Indeed it would seem logical to have all
>> commands showing diffs (diff, add -p, log -p, reset -p, etc..) respect
>> the diff options.
>
> Here's a patch to do so, similar to what we do for diff.algorithm.
>
> -- >8 --
> Subject: add--interactive: respect diff.compactionHeuristic
>
> We use plumbing to generate the diff, so it doesn't
> automatically pick up UI config like compactionHeuristic.
> Let's forward it on, since interactive adding is porcelain.
>
> Note that we only need to handle the "true" case. There's no
> point in passing --no-compaction-heuristic when the variable
> is false, since nothing else could have turned it on.

>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  git-add--interactive.perl | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/git-add--interactive.perl b/git-add--interactive.perl
> index 822f857..642cce1 100755
> --- a/git-add--interactive.perl
> +++ b/git-add--interactive.perl
> @@ -45,6 +45,7 @@ my ($diff_new_color) =
>  my $normal_color = $repo->get_color("", "reset");
>
>  my $diff_algorithm = $repo->config('diff.algorithm');
> +my $diff_compaction_heuristic = $repo->config_bool('diff.compactionheuristic');
>  my $diff_filter = $repo->config('interactive.difffilter');
>
>  my $use_readkey = 0;
> @@ -749,6 +750,9 @@ sub parse_diff {
>         if (defined $diff_algorithm) {
>                 splice @diff_cmd, 1, 0, "--diff-algorithm=${diff_algorithm}";
>         }
> +       if ($diff_compaction_heuristic) {
> +               splice @diff_cmd, 1, 0, "--compaction-heuristic";
> +       }
>         if (defined $patch_mode_revision) {
>                 push @diff_cmd, get_diff_reference($patch_mode_revision);
>         }
> --
> 2.9.0.160.g4984cba
>
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> > -- >8 --
> > Subject: add--interactive: respect diff.compactionHeuristic
> >
> > We use plumbing to generate the diff, so it doesn't
> > automatically pick up UI config like compactionHeuristic.
> > Let's forward it on, since interactive adding is porcelain.
> >
> > Note that we only need to handle the "true" case. There's no
> > point in passing --no-compaction-heuristic when the variable
> > is false, since nothing else could have turned it on.
> 
> because we don't want to implement --[no-]compaction-heuristic
> as a command line switch to git-add?
> Fine with me.

> Stepping back and looking how the compaction heuristic turned out,
> I think this is what we did not want to see, i.e. the need to bring it in
> every command, but rather enable and release it. But we backed off
> of the default-on, and now people may ask for the  --no-compaction-heuristic
> in interactive add eventually, when they run into a corner case.