Re: [PATCH v3 2/2] range-diff: fix regression in passing along diff options

On Fri, Nov 09 2018, Eric Sunshine wrote:

On Thu, Nov 8, 2018 at 5:34 PM Ævar Arnfjörð Bjarmason [off-list ref] wrote:

quoted

On Thu, Nov 08 2018, Eric Sunshine wrote:

quoted

Looking at diff.c:parse_diff_opt() and enable_patch_output(), rather
than introducing this new conditional, I'm thinking that a more
correct fix would be:

    opts.output_format |= DIFF_FORMAT_PATCH;

(note the '|=' operator). This would result in 'opts.output_format'
containing (DIFF_FORMAT_PATCH | DIFF_FORMAT_NO_OUTPUT), just as it did
prior to 73a834e9e2 when --no-patch was specified.

Maybe I'm misunderstanding, but if you mean this on top:

    -               if (!opts.output_format)
    -                       opts.output_format = DIFF_FORMAT_PATCH;
    +               opts.output_format |= DIFF_FORMAT_PATCH;

That is indeed what I mean.

*Nod*

quoted

Then the --stat test I've added here fails, because unlike "diff" the
"--stat" (and others) will implicitly "--patch" and you need
"--no-patch" as well (again, unlike with "diff").

This new --stat test also fails with Dscho's original git-range-diff
implementation, even before 73a834e9e2 regressed the --no-patch case.
The commit message seems to sell this patch as a pure regression-fix,
so it feels wrong for it to be conflating a regression fix
(--no-patch) with preparation for potential future improvements to
other options (--stat, etc.).

I could see this as a two-patch series in which patch 1/2 fixes the
regression (with, say, "|="), and patch 2/2 generalizes setting
'opts.output_format' for the future. Alternately, if left as a single
patch, perhaps the commit message could be fleshed out to better
explain that it is doing more than merely fixing a regression (since
it wasn't at all obvious to me, even after digging into the code
earlier to come up with "|=", or now when trying to understand your
response).

Yeah that makes sense. I did not see (but see now) that the --stat
behavior was different now v.s. before your 73a834e9e2.

quoted

Right now --stat is pretty useless, but it could be made to make sense,
and at that point (and earlier) I think it would be confusing if
"range-diff" had different semantics with no options v.s. one option
like "--stat" v.s. "--stat -p" compared to "diff".

Perhaps this sort of rationale, along with some explanatory examples
could be added to the commit message to help the reader more fully
understand the situation.

*Nod*