Cannot clone with a reference to a tag

[fkorotkov]

I'm using the following snippet to clone a single tag:

func main() {
	cloneDirPtr := flag.String("clone-dir", os.Args[0], "Directory to clone")
	cloneUrlPtr := flag.String("clone-url", "https://github.com/fkorotkov/k8s-kotlin-dsl.git", "URL to clone")
	flag.Parse()

	cloneOptions := git.CloneOptions{
		URL:           *cloneUrlPtr,
		ReferenceName: plumbing.ReferenceName("refs/tags/0.9"),
		SingleBranch:  true,
		Progress:      os.Stdout,
		Tags:          git.NoTags,
	}
	_, err := git.PlainClone(*cloneDirPtr, false, &cloneOptions)
	CheckIfError(err)
}

After cloning to temp directory I did the following:

fedor-mbp master$: cd temp/
fedor-mbp HEAD$: git branch -a
* (no branch)

If I change ref from refs/tags/0.9 to refs/heads/master and do the same I see:

fedor-mbp master$: cd temp/
fedor-mbp master$: git branch -a
* master
  remotes/origin/master

Git correctly sees that master branch is checked out. I'd expect the same behaviour for tag refs.

[smola]

@fkorotkov I'm not sure what's the problem here. Git tags and branches are non-overlapping concepts. Git never sees tags as branches. Are you able to reproduce your desired behavior using the git command line?

[fkorotkov]

git clone -b 0.9 --single-branch https://github.com/fkorotkov/k8s-kotlin-dsl.git

Indeed has the same behaviour.

[fkorotkov]

@smola I've took another look and seems the behaviour is not quite the same when using go-git. I've tried:

fedor-mbp master$: go run main.go --clone-dir=temp
fedor-mbp master$: cd temp/
fedor-mbp HEAD$: git fetch origin
fatal: Couldn't find remote ref refs/heads/0.9

Where if do clone via regular git:

fedor-mbp $: git clone -b 0.9 --single-branch https://github.com/fkorotkov/k8s-kotlin-dsl.git
...
fedor-mbp $: cd k8s-kotlin-dsl/
fedor-mbp HEAD$: git fetch origin

[smola]

@fkorotkov Thank you! That looks like a bug, indeed. I changed the title to a more accurate one.

[fkorotkov]

@smola do you have a clue where the problem can be? I've tried to investigate but I don't have enough knowledge about go-git yet. Will appreciate a hint.

I've tried to understand where Couldn't find remote ref refs/heads/0.9 can come from since ref is not correct for a tag but my debugging session didn't lead to anything useful.

[smola]

@fkorotkov A tag is a reference too, but when cloning, tags have some specific logic that is probably breaking this. The error comes from here:

go-git/remote.go

Line 685 in 41d6f2c

return fmt.Errorf("couldn't find remote ref %q", s.Src())

I didn't give a look in depth yet, though.

[fkorotkov]

This error comes from a normal Git.

I diffed two folders (one by Git and one by go-git) and found a difference in .git/config:

<       fetch = +refs/heads/0.9:refs/remotes/origin/0.9
---
>       fetch = +refs/tags/0.9:refs/tags/0.9