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

Jeff King [off-list ref] writes:

On Wed, Aug 05, 2020 at 01:06:51AM +0300, Sergey Organov wrote:

quoted

quoted

For now, "off" is OK, but then we'll regret when "all" comes,
because "off" would not exactly sit opposite to "all".

IMHO, "off" does not need to be opposite for "all", as it suppresses
diff output altogether. I read --diff-merge=off as "turn /off/ diff
output for merge commits".

Besides, "all", that I don't like either, is among "c" and "cc", all 3
being different versions of diffs against all the parents, no?

I think "all-parents" is much more descriptive than "all" (which might
make you think "all merges", but it has nothing to do with that). It
would make more sense if we later add the building to say "diff against
parent 1" or "diff against parents 1 and 3".

You might also consider whether "combined" is actually mutually
exclusive with parent selection. We have focused on which parents you'd
want to "-m" against. But in the most general case, you could ask for a
combined-diff between parents 1 and 3 of an octopus merge.

That's just coming from the angle of "what is the most general and
orthogonal set of features". I think the vast majority of what anyone
would want to do would be covered by doing a diff against only a single
parent, and then it would almost always be the first parent. And
certainly you'd need to add a bunch of code to the combined diff
machinery to make it support arbitrary sets of parents. So this probably
isn't that interesting a direction to go, at least for now. I'm just
raising the issue now because we'll be locked into the semantics of this
option, which may not be able to express the full set of what's possible
(so we'd be stuck adding another option later).

Makes sense, and I got an idea.

--diff-merges=<parent> will still give diff against one specific parent.

In case of combined/separate diffs, it will produce diffs against all
the parents that, if happens to be needed, could later be refined by a
new --diff-parents option that defaults to 'all'.

Then, for example,

--diff-merges=1

would finally be just a short-cut for

--diff-merges=separate --diff-parents=1

while

--diff-merges=separate --diff-parents=all

would be the same as

--diff-merges=separate (what we called "all" so far)

and then we may have

--diff-merges=condensed-combined --diff-parents=1-3,8

for the bravest ;-)

This would lead us, currently to:

--diff-merges=(off,separate,combined,condensed-combined,<parent>)

and leave us ability to implement advanced parents selection, in an
unlikely case it's needed, in a separate new option.

Thanks,
-- Sergey