Fix opening files for branches' upstreams
Fix opening files for branches' upstreams

Previously if you had a branch `foo` that tracked upstream `main` we
would open `blob/foo/file/path` instead of `blob/main/file/path`. Since
`foo` is only the local branch name this was invalid.

keith/dotfiles,keith/dotfiles,keith/dotfiles,keith/dotfiles,keith/dotfiles,keith/dotfiles