Re: [PATCH 0/2] merge-tree: add new --mergeability-only option

[Elijah Newren <newren@gmail.com>]

On Mon, May 12, 2025 at 11:27 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> Elijah Newren <newren@gmail.com> writes:
>
> > I thought about that, but I was worried that folks would expect
> > "--dry-run" to not make any changes.  This mode does not prevent
> > writing objects to the object store, it merely avoids it in the "outer
> > layer" of the merge.
>
> I think we have already precedence to call something that creates
> new objects in the object database, as long as the resulting objects
> are not made reachable ("git fetch --dry-run" probably falls into
> that category).  The idea is that it does not make a change that is
> "observable" by end-users (and what "gc" sees is not part of what
> the users would be observaing).

Oh, I was unaware of `git fetch --dry-run` for some reason.  And its
documentation even states "without making any changes" despite the
fact that it downloads more objects to the object store, so it indeed
sounds like a good precedent.

I'll switch the flag name to --dry-run.  (I have a suspicion, however,
that the primary users of this new merge-tree flag will care about
whether objects are created, so I still want the documentation to call
it out, unlike git fetch's --dry-run option.)

> We have "--check" (in "git apply"), which is an exact counterpart in
> the patch based workflow to this thing.  It reads
>
>         Instead of applying the patch, see if the patch is
>         applicable to the current working tree and/or the index
>         file and detects errors.  Turns off "apply".
>
> I feel that `apply --check` should have been `apply --dry-run`, so I
> would not recommend calling it `--check` for `merge-tree`, though.

Makes sense; thanks for the pointers.