merge-ort and --rebase-merges, was Re: [PATCH v2 0/7] Drop support for git rebase --preserve-merges

Hi Elijah,

On Fri, 10 Sep 2021, Elijah Newren wrote:

On Fri, Sep 10, 2021 at 5:08 AM Johannes Schindelin
[off-list ref] wrote:

quoted

On Tue, 7 Sep 2021, Elijah Newren wrote:

quoted

On Tue, Sep 7, 2021 at 11:51 AM Johannes Schindelin
[off-list ref] wrote:

[... talk about re-resolving merge conflicts when recreating merges
 in a `git rebase --rebase-merges` run ...]

...

quoted

While I agree that `merge-ort` makes a lot of things much better, I think
in this context we need to keep in mind that those nested merge conflicts
can really hurt.

Yes, and I'm not sure you fully appreciate how much either.

*grin*

[... a lot of insight that I totally agree with ...]

I believe the commit graph you were describing was this:

* rebase-of-original-merge
|\
| * rebase-of-local-add-caller-of-core
* | rebase-of-local-rename-to-hi
|/
* upstream
|
|
|
| * original-merge
| |\
| | * local-add-caller-of-core
| |/
|/|
| * local-rename-to-hi
|/
* initial-version


Further, the versions of main.c in each of those are as follows:

==> initial-version:
int core(void) {
    printf("Hello, world!\n");
}


==> local-rename-to-hi:
int hi(void) {
    printf("Hello, world!\n");
}


==> local-add-caller-of-core:
int core(void) {
    printf("Hello, world!\n");
}
/* caller */
void caller(void) {
    core();
}


==> what an automatic merge of the two local-* branches would give:
int hi(void) {
    printf("Hello, world!\n");
}
/* caller */
void caller(void) {
    core();
}


==> original-merge (amended from above by s/core/hi/ in caller()):
int hi(void) {
    printf("Hello, world!\n");
}
/* caller */
void caller(void) {
    hi();
}


==> upstream:
int greeting(void) {
    printf("Hello, world!\n");
}
/* main event loop */
void event_loop(void) {
    /* TODO: place holder for now */
}


==> rebase-of-local-rename-to-hi (kept 'hi' over 'greeting'):
int hi(void) {
    printf("Hello, world!\n");
}
/* main event loop */
void event_loop(void) {
    /* TODO: place holder for now */
}


==> rebase-of-local-add-caller-of-core (kept both new functions,
updated caller):
int greeting(void) {
    printf("Hello, world!\n");
}
/* main event loop */
void event_loop(void) {
    /* TODO: place holder for now */
}
/* caller */
void caller(void) {
    greeting();
}

That all matches my recollection of what I wanted to drive at.

If I've understood that all correctly, then my idea will give you the
following conflict to resolve:

==> rebase-of-original-merge, before conflict resolution:
int hi(void) {
    printf("Hello, world!\n");
}
/* main event loop */
void event_loop(void) {
    /* TODO: place holder for now */
}
/* caller */
void caller(void) {
<<<<<<< HEAD
    greeting();
||||||| auto-remerge of original-merge
    core();
=======
    hi();

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original-merge

}

That looks very intriguing! I would _love_ to play with this a bit, and I
think you provided enough guidance to get going. I am currently preparing
to go mostly offline for the second half of September, read: I won't be
able to play with this before October. But I am definitely interested,
this sounds very exciting.

Ciao,
Dscho