Revset to identify a megamerge

[9999years]

With the jj megamerge workflow, I'd like to have a command to create a new stream of work from the working commit. Currently, this looks like jj split -A 'trunk()' -B my_megamerge ..

I'd like to write a revset alias that identifies the megamerge commit.

Here’s the best i’ve got so far, but it doesn’t work reliably if you have multiple megamerges or if you have commits that merge with each other as ancestors of the megamerge commit.

revset-aliases.M = "latest(merges() & mine() & mutable() & fork_point(trunk() | @)::, 1)"

Is there a way to get the ‘descendent-most’ commit from a set of commits? (E.g. from a revset get a commit that doesn't have any of the other commits as a descendant?)

[jennings]

I am cheesy and I usually just jj describe -m "merge" my mega-merges, then I can select it with description(exact:"merge").

[chriskrycho]

I’m similar: I use [integration merge] and that’s super easy to use for a revset selector. (It’s also in my private revsets so I don’t push it by default.)

[jennings]

I've started using megamerges more often and gotten lazy about naming them, so I've added this alias to find the "closest" megamerge to @:

[revset-aliases]
'mega' = 'heads(merges() & ::@)'

I use it most often like this to insert a new commit between main and the megamerge:

$ jj squash -A main -B mega

(I actually have exactly(heads(merges() & ::@)) in my config, but now that I'm writing it here, I don't think heads(merges() & ::@) can ever resolve to more than one revision anyway.)

[9999years]

jj squash can insert a new commit ?? I've been using jj split -A T -B M . for that!

[jennings]

Yeah, confusingly enough, jj split and jj squash are nearly the same command nowadays even though they have opposite behavior by default. Split defaults to essentially -i -d @ and squash defaults to --into @-.

[9999years]

Cool! I was definitely surprised when I learned you can specify both -A and -B to create a commit between two other commits. But it makes a lot of sense.

[9999years]

@lilyball shared her revset for identifying a megamerge (which she calls stack_point()), so I thought I'd share it here. The great insight here is reachable(@, mutable()), which only considers mutable commits that are connected to the working commit:

revset-aliases."stack_point()" = "exactly(coalesce(@ & merges(), heads(reachable(@, mutable()) & merges())), 1)";