Fix instruction order on "Co-authored-by" support

[bengtrj]

I might be wrong, but I think the order needs to be changed. In my mac it only worked after running git init and then git duet. It might be related to the hook file.
May I suggest a diagram/state-machine on how the whole thing works? Thanks!

[ansd]

@bengtrj, the documentation assumes that your current working directory is an existing git repo. (Maybe that's the part which is missing in the docs?)

You first run git duet in that repo.

If GIT_DUET_GLOBAL is set, it will install the hook into $HOME/.git-template which requires you to run git init subsequently in order to copy the hook file from $HOME/.git-template into your git repo. (Running git init here does not initialise an empty repo but rather reinitialises your existing repo.)

If GIT_DUET_GLOBAL is not set, there is no need to run git init because the hook gets installed directly into your git repo.