Re: [RFC] Rebasing merges: a jorney to the ultimate solution(RoadClear)

[Igor Djordjevic <igor.d.djordjevic@gmail.com>]

Hi Dscho,

On 11/03/2018 13:00, Johannes Schindelin wrote:
> 
> > I actually like `pick` for _rebasing_ merge commits, as `pick` is 
> > already used for rebasing non-merge commits, too, so it feels natural.
> 
> Phillip is right, though: this would repeat the design mistake of
> --preserve-merges.
> 
> We must not forget that the interactive mode is the target here, and that
> the syntax (as well as the generated todo list) must allow for easy
> modification. The `pick <merge>` approach does not allow that, so we
> cannot use it.
> 
> The `merge -R -C <original-commit> <merge-head>` approach is a lot better:
> it offers the flexibility, without sacrificing the ease when not modifying
> the todo list.

Eh, I`m afraid the quote you took is missing the rest of its 
(important) context, where I mentioned already proposed format for 
`pick` in that other subthread[1], including other parameters beside 
merge commit to pick, as that parent mapping.

I agree with both of you that `pick <merge-commit>` is inflexible 
(not to say just plain wrong), but I never thought about it like that.

If we are to extract further mentioned explicit old:new merge 
parameter mapping to a separate discussion point, what we`re 
eventually left with is just replacing this:

	merge -R -C <original--merge-commit> <merge-head>

... with this:

	pick <original--merge-commit> <merge-head>


That is what I had in mind, seeming possibly more straightforward and 
beautifully aligned with previously existing (and well known) 
`rebase` terminology.

Not to say this would make it possible to use other `rebase -i` todo 
list commands, too, like if you want to amend/edit merge commit after 
it was rebased, you would write:

	edit <original--merge-commit> <merge-head>

..., where in case you would simply like to reword its commit 
message, it would be just:

	reword <original--merge-commit> <merge-head>


Even `squash` and `fixup` could have their place in combination with 
a (to be rebased) merge commit, albeit in a pretty exotic rebases, 
thus these could probably be just disallowed - for the time being, at 
least.

The real power would be buried in implementation, learning to rebase 
merge commits, so user is left with a very familiar interface, slightly 
adapted do accommodate a bit different nature of merge commit in 
comparison to an ordinary one, also to allow a bit more of interactive 
rebase functionality, but it would pretty much stay the same, without 
even a need to learn about new `merge`, `-R`, `-C`, and so on.

Yes, those would have its purpose, but for real merging then 
(creating new merges, or recreating old ones), not necessarily for 
merge rebasing.

With state of `merge -R -C ...` (that `-R` being the culprit), it 
kind of feels like we`re now trying to bolt "rebase merges" 
functionality onto a totally different one (recreate merges, serving 
a different purpose), making them both needlessly dependent on each 
other, further complicating user interface, making it more confusing 
and less tunable as per each separate functionality needs (rebase vs. 
recreate).

I guess I`m the one to pretty much blame here, too, as I really 
wanted `--recreate-merges` to handle "rebase merges" better, only to 
later realize it might not be the best tool for the job, and that a 
more separate approach would be better (at least not through the same 
`merge` todo list command)...

Regards, Buga

[1] https://public-inbox.org/git/f3872fb9-01bc-b2f1-aee9-cfc0e4db77d6@gmail.com/