Re: [PATCH v2 0/7] making log --first-parent imply -m

Jeff King [off-list ref] writes:

On Thu, Jul 30, 2020 at 12:41:39AM +0300, Sergey Organov wrote:

quoted

quoted

Here's a re-roll taking into account the discussion so far:

  - the escape hatch option name is flipped to "--no-diff-merges" (with
    "--diff-merges" matching "-m")

Rather than being just a synonym for -m, is there a chance for
"--diff-merges" implementation to be turned to output diff to the first
parent only, no matter if --first-parent is active or not?

Alternatively, may it have a parameter such as "-m parent-number" of
"git cherry-pick" being set to "1" by default?

Yes, I agree that would be a useful feature, but I don't think it needs
to be part of this series. It could be implemented as --diff-merges=1 to
show only the one against the first parent, or as its own option. But we
can add that on top.

quoted

This -m output of diffs to all the parents is in fact primary source of
confusion for me, even over all these mind-blowing inter-dependencies
between --first-parent, --cc, -c, -m, -p and what not. Who ever needs
these (potentially huge) diffs against other parents, anyway?

I've used "-m" second-parent diffs occasionally for hunting down
mismerges, etc, but I agree that most of the time you just want to see
the diff against the first parent.

quoted

Introduction of this new option is a great opportunity for improvement
that would be a pity to miss.

Adding an optional value to the flag is something we can do later. We
would miss the opportunity for "--diff-merges" to default to
"--diff-merges=1", but I'm not sure I'd want to do that anyway. Having
it be consistent with "-m" seems less confusing to me, and it is already
too late to change that.

If we want an option that defaults to "1", we can give it a new name.
The only thing that is lost now is that --diff-merges would already be
taken. :) But I think I'd probably call such an option "--diff-parents"
or something like that anyway.

Yeah, I see your point, thanks for considering!

What I in fact have in mind is something like:

  --diff-merges[=<parent-number>|c|cc|all]

to have a single point of definition of the needed format of merges
representation.

Then comes the question of the default. "all" is what'd make it behave
as "-m" behaves now. If it's too late for --diff-merges to have
different default, could the default possibly be a configuration
option rather than yet another command-line option?

-- Sergey