Git clone fails with "fatal: multiple updates for ref 'refs/tags/v1.0.0' not allowed" on MacOS Mojave
Do you have a custom .gitconfig? I had to remove the following parameter from mine in order for cloning to work again:

[remote "origin"]
    fetch = +refs/heads/*:refs/remotes/origin/*


git v2.21.0 was released a few days ago, so perhaps something changed under the hood. I need to go check out the release notes. 

Anyways, hope this helps!



Adding a bit more background context, this line was very common to fetch the tags by default. It allowed to do git fetch which would also do a git fetch --tags equivalent under the hood.

Basically, if you want to fetch tags when you do a git fetch with this v2.21 git version, you can create an alias in your .gitconfig as follow:

[alias]
    fetch = git fetch --tags


Doing this and removing the fetch = +refs/heads/*:refs/remotes/origin/* will result in the same behaviour, but compatible with git v2.21

See https://stackoverflow.com/questions/1204190/does-git-fetch-tags-include-git-fetch/20608181#20608181 for in-depth explanation and history changes.