Xcode 11 - "Couldn't communicate with a helper application." when attempting to add Swift Package

I've finally worked out what this was. I had something in my ~/.gitconfig file which Xcode obviously did't like.

I worked this out by removing the ~/.gitconfig and then retrying (and it worked). Then I tried removing parts of the ~/.gitconfig contents bit by bit.

Evntually I idenitified that this was the section causing the issue.

[includeIf "gitdir:~/some/path/"]
    path = "~/some/path/.gitconfig_include"

This section works in other contexts. No idea why it causes Xcode to barf.