go-git fails to parse branches with refs/pull as their merge target

[georgettica]

as a user of go-git, it seems the command https://pkg.go.dev/github.com/go-git/go-git/v5#Repository.ConfigScoped fails for gh pr checkout remote branches (from other users)

tools used for test:

• https://github.com/georgettica/gogitmail
  • go-git as a library I use it gogitmail
• https://github.com/cli/cli

$ gh repo fork --clone 
$ gh pr checkout ${PR_NUMBER}
...
$ cat .git/config
...
[branch "master"]
        remote = upstream
        pushRemote = upstream
        merge = refs/pull/${PR_NUMBER}/head
...
$ gogitmail
panic: branch config: invalid merge

the issue stems from the fact that refs/pull is not a valid merge target, but is what cli/cli pushes.

LOC that fails in go-git

go-git/plumbing/reference.go

Line 90 in 69aa78a

return strings.HasPrefix(string(r), refHeadPrefix)

LOC that fails in my code https://github.com/georgettica/gogitmail/blob/38ccca86d8503101686497c63b21a48c71f81380/pkg/utils/utils.go#L24

---

I cannot check the error for the string there as it's an internal error

[Skarlso]

This works fine:

	if err := r.Fetch(&git.FetchOptions{
		RefSpecs: []config.RefSpec{"refs/pull/3741/head:suspend_asg_processes"},
		Depth:    1,
	}); err != nil {
		fmt.Println("fetch err: ", err)
		os.Exit(1)
	}

[georgettica]

Lost context on this a long time ago, I hope this doesn't happen to anyone else bit if it does now there is a snippet :)

I'll see if I get to testing this in my code :)

[MichaelMure]

It happened to me as well in the context of https://github.com/MichaelMure/git-bug, where I don't control the user git config, yet want to read or add values there.