Re: [PATCH v4 3/3] replay: offer an option to linearize the commit topology

> On Fri, Jun 26, 2026 at 07:36:31AM +0200, Toon Claes wrote:
> > Patrick Steinhardt <ps@pks.im> writes:
> > 
> > > git-rebase(1) essentially knows about three different modes:
> > >
> > >   - "--no-rebase-merges", which is the default and maps to your
> > >     "--linearize".
> > >
> > >   - "--rebase-merges", which by default doesn't rebase cousins by using
> > >     "--ancestry-path" internally.
> > >
> > >   - "--rebase-merges=rebase-cousins", which doesn't pass the above
> > >     option.
> > >
> > > So it's not a simple boolean there, which makes me wonder whether we
> > > should mirror the same interface so that all of git-rebase(1)'s modes
> > > can be represented, as well.
> > 
> > That's a valid question, although I don't know a good answer to that.
> > 
> > Basically you're asking for what the command line options will look
> > like? Allow me to think out loud.
> > 
> > In this series I'm adding --linearize to git-replay(1). As mentioned, I
> > don't think it makes sense to add it to git-history(1) as well. Without
> > this option, the process aborts when it encounters a merge.
> > 
> > Dscho sent a patch series to properly replay (2-way) merges. I think
> > this should become the default for both git-replay(1) and
> > git-history(1).
> > 
> > But then, do we want to have an option that brings back the current
> > behavior of aborting at merges? Maybe with --no-merges?
> 
> I think that would be a sensible option to have.

> > Then there's the option of rebasing cousins left. That's something that
> > isn't covered by Dscho's series yet. Maybe --replay-cousins?
> > 
> > To reiterate what the final design could look like:
> > 
> >  * <nothing>: replay merges preserving topology.
> >  * "--linearize": flattens merges (only git-replay(1)).
> >  * "--no-merges": dies when the process tries to replay a merge.
> >  * "--replay-cousins": does what --rebase-merges=rebase-cousins does.
> 
> Right. And if we tried to be consistent with git-rebase(1), then this
> could be done as:
> 
>   - "--rebase-merges" to replay merges preserving topology, which is the
>     default once we support replaying them.
> 
>   - "--no-rebase-merges" to flatten commits.
> 
>   - "--rebase-merges=abort" to explicitly die when seeing merges.
> 
>   - "--rebase-merges=rebase-cousins"

> > Now, all these options are (I think) mutually exclusive, so we could
> > consider an option "--replay-merges=<mode>", but personally I find
> > "--<option>=<value>" arguments harder to use than specifying separate
> > options.
> > 
> > I think I'm avoiding your question, because the design of the command
> > line parameters doesn't need tot 1-on-1 correlate to the internal
> > datastructure. And I agree the mode isn't a boolean, but does that mean
> > we want to use an enum internally? Well, I don't know. And I also don't
> > think that matters right now. Code is easy to change, I think the
> > command line options should be designed with the future in mind, which I
> > believe we do with "--linearize".
> > 
> > Sorry for this long-winded rambling, but bottom line I think it's fine
> > to add --linearize and in the future add more options and see how the
> > code should evolve to support those.
> 
> Hm, I dunno. You basically reasoned that we potentially want to have all
> of the same options that git-rebase(1)'s "--rebase-merges=" already
> supports. So that begs the question why we need to reinvent the wheel
> then and not just use the same syntax.

> Note that I'm not arguing that we should support all of these options
> now. I'm merely arguing that we should try to be consistent, unless
> there is a good argument not to do that. I'm fine with the interface if
> there indeed is a good argument, but if so we should document why we
> think that the current interface in git-rebase(1) is not a good fit for
> this command.
> 
> Thanks!
> 
> Patrick
> 
>