Suppress "detached head" advice during checkout

[jeffwidman]

Checking out certain ref values will result in a warning about a detached HEAD:

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

However, this warning isn't useful in a CI environment... so suppress it.

I realize on the original bug report that one user mentioned this warning highlighted a bug in his actions flow, but I consider that a super rare / happy accident. 99% of use cases will be intentionally checking out a specific ref where the detached head state is inevitable, so the warning is pure noise.

Passing the config this way sets it only for this command. Note that it must be set before calling checkout.

Resolve: #494

[jeffwidman]

I'm not very familiar with typescript, so unclear if I need to also compile this to the javascript dst code.

Happy to do that if you let me know what I need to do.

[Frieder-AirLST]

I have an issue in my flow right now. the message you want to suppress brought me here... please do not disable it by default.