Can't upload merge commit to Gerrit

[avm99963]

When attempting to upload a merge commit to Gerrit, I get the following error:

Error: Refusing to upload revision xotlnknluvyt because it is empty
Hint: Perhaps you squashed then ran upload? Maybe you meant to upload the parent commit instead (eg. @-)

jj/cli/src/commands/gerrit/upload.rs

Lines 220 to 231 in aa2f1be

	// Immediately error and reject any commits that shouldn't be uploaded.
	for commit in &to_upload {
	if commit.is_empty(tx.repo_mut())? {
	return Err(user_error(format!(
	"Refusing to upload revision {} because it is empty",
	short_change_hash(commit.change_id())
	))
	.hinted(
	"Perhaps you squashed then ran upload? Maybe you meant to upload the parent \
	commit instead (eg. @-)",
	));
	}

I saw that the check was added in a commit written by @thoughtpolice (thanks btw, I've been following the progress since your first PR and it's great to finally have Gerrit support in Jujutsu!!).

Do you think we could be able to relax this condition? I don't know if it's simply to warn the user of a possible unintended upload, or if there is something else that I'm missing.

Thanks in advance! :)

[jennings]

I don't have a lot of experience with Gerrit, but I thought it essentially avoided merges because it cherry picks your changes into the target branch when it's submitted.

The merge commit being empty means there's nothing in it to review (there are no conflict resolutions in it), so why do you need to submit that to Gerrit?

[avm99963]

Thanks for you comment, @jennings!

I don't have a lot of experience with Gerrit, but I thought it essentially avoided merges because it cherry picks your changes into the target branch when it's submitted.

Indeed, and for me this is one of the selling points of Gerrit! When submitting a Gerrit change/commit, it is usually rebased into the target branch and the branch is fast-forwarded (so, similar to a cherry-pick as you say).¹

The merge commit being empty means there's nothing in it to review (there are no conflict resolutions in it), so why do you need to submit that to Gerrit?

I had 2 out-of-date branches, and I wanted to merge one into the other one. So I created a merge commit with JJ, and tried to upload it to Gerrit with JJ. That was when I stumbled upon this.

Here's a sample merge commit from the official Gerrit development instance: https://gerrit-review.googlesource.com/c/gerrit/+/546841. With JJ I wouldn't be able to upload that commit.

Footnotes

1. In reality, there are multiple submit strategies in Gerrit. So changes/commits can also be merged into the target branch if someone so wished, but I honestly don't see why one would prefer this behavior. ↩

[jennings]

Here's a sample merge commit from the official Gerrit development instance: https://gerrit-review.googlesource.com/c/gerrit/+/546841. With JJ I wouldn't be able to upload that commit.

Oh interesting, I was only thinking about landing new work. I didn't even consider integrating long-running branches. That makes sense, thanks!

[jakubsmolaga]

I have also run into this, are there any solutions or do I just have to use git?