Unable to update git repos where default branch name has '/'

[ealap]

Describe the bug

znap pull fails when a plugin repo has a default branch that has '/' in its name.

Steps To Reproduce

1. znap source 'ealap/zsh-abbr' # default branch is 'dev/ealap/main'
2. znap pull

Expected behavior

znap pull can successfully update the plugin

Observed behavior

An error occurs.

ealap/zsh-abbr couldn't find remote ref dev
no upstream

It seems to be only using the string before the first '/'

Environment:

• OS: macOS, debian
• Terminal: alacritty
• Zsh version: 5.9
• Repo version: main f8685ea

Additional context

A quick scan of the code tells me the problem likely comes from here but I don't understand it fully yet.
https://github.com/marlonrichert/zsh-snap/blame/f8685ea5933335ea4cbd54780ace16ef85c346bd/functions/..znap.fetch#L12

Workaround for me now is to just use a simple branch name as default for my forked repos.