Re: [PATCH 1/1] remote.c: fix handling of push:remote_ref

From: Jeff King <peff@peff.net>
Date: Mar 2, 2020, 13:48 UTC
Message-ID: <20200302134842.GB1176622@coredump.intra.peff.net>
In-Reply-To: <20200301220531.iuokzzdb5gruslrn@doriath>

On Sun, Mar 01, 2020 at 11:05:31PM +0100, Damien Robert wrote:

> So it remains the problem of handling the 'upstream' case.
> The ideal solution would be to not duplicate branch_get_push_1.

Yeah, that would be nice (though at least if it's all contained in remote.c, we can live with some duplication). There's already some duplication in the way remote_ref_for_branch() applies remote refspecs.

And I think all of this may be duplicated with git-push itself (which would also be nice to get rid of, but last time I looked into it was hard to refactor it to do so).

Show 7 quoted lines

> In most of the case, this function finds `dst` which is exactly the
> push:remoteref we are looking for.
> 
> Then branch_get_push_1 uses
> 		ret = tracking_for_push_dest(remote, dst, err);
> which simply calls
> 	ret = apply_refspecs(&remote->fetch, dst);

Right, there we already have the remote name, and are applying the fetch refspecs to know what our tracking branch would be. So in remote_ref_for_branch(), we'd just not apply those.

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> The only different case is
> 	case PUSH_DEFAULT_UPSTREAM:
> 		return branch_get_upstream(branch, err);
> which returns
> 	branch->merge[0]->dst

We also have PUSH_DEFAULT_NOTHING, for which obviously we'd return nothing (NULL or an empty string).

Likewise for SIMPLE, we probably need to check that the upstream has a matching name (and return nothing if not).

> So we could almost write an auxiliary function that returns push:remoteref
> and use it both in remote_ref_for_branch and branch_get_push_1 (via a
> further call to tracking_for_push_dest) except for the 'upstream' case
> which is subtly different.

Yes, that makes sense.

> In the 'upstream' case, the auxiliary function would return
> branch->merge_name[0]. So the question is: can
> tracking_for_push_dest(branch->merge_name[0]) be different from
> branch->merge[0]->dst?

Those will both return tracking refs. I think you just want merge[0]->src for the upstream case.

And yes, the two can be different. It's the same case as when the upstream branch has a different name than the current branch.

> Another solution could be as follow: we already store `push` in
> `branch->push_tracking_ref`. So the question is: can we always easily convert
> something like refs/remotes/origin/branch_name to refs/heads/branch_name
> (ie essentially reverse ètracking_for_push_dest`), or are there corner cases?

This would basically be reverse-applying the fetch refspec. In theory it should be possible, but there are cases where somebody has overlapping refspecs. But at any rate, I think it's better to just get the pre-mapped values (i.e., avoid calling tracking_for_push_dest() in the first place).

> Otherwise a simple but not elegant solution would be to copy paste the
> code of branch_get_push_1 to remote_ref_for_branch, simply removing the
> calls to `tracking_for_push_dest` and using remote->branch_name[0] rather
> than remote->branch[0]->dst for the upstream case.

Yeah, I think that's going to be the easiest. It would be nice to avoid repeating that switch(), but frankly I think the boilerplate you'll end up with trying to handle the two cases may be worse than just repeating it. It may be worth adding a comment to each function to mention the other, and that any changes need to match.

-Peff