Attempting to create a new worktree from a branch pulled from remote fails

[mminns]

At the moment the extension will not detect tht this is an existing branch, instead it will attempt to create a new branch with the same name.

This is only prevent by checking out the target branch first, which undermines the efficiency of using this extension

[mminns]

Use the following first to get the remote branch
git fetch origin {branchname}

if it fails don't worry as it might be a local branch