You have the config for this task:
Set the desired message off by setting the config value to false:
# turn the detached message off
git config --global advice.detachedHead false
detachedHead
Advice shown when you used git-checkout(1) to move to the detach HEAD state, to instruct how to create a local branch after the fact.
advice.*
These variables control various optional help messages designed to aid new users. All advice.* variables default to true, and you can tell Git that you do not need help by setting these to false:
You can set any of the following after the advice:
git config --global advice.<...>
pushUpdateRejected
Set this variable to false if you want to disable
pushNonFFCurrent,
pushNonFFMatching,
pushAlreadyExists,
pushFetchFirst, and
pushNeedsForce simultaneously.
pushNonFFCurrent
Advice shown when git-push(1) fails due to a non-fast-forward update
to the current branch.
pushNonFFMatching
Advice shown when you ran git-push(1) and pushed matching refs
explicitly (i.e. you used :, or specified a refspec that isn’t your
current branch) and it resulted in a non-fast-forward error.
pushAlreadyExists
Shown when git-push(1) rejects an update that does not qualify
for fast-forwarding (e.g., a tag.)
pushFetchFirst
Shown when git-push(1) rejects an update that tries to overwrite a
remote ref that points at an object we do not have.
pushNeedsForce
Shown when git-push(1) rejects an update that tries to overwrite a
remote ref that points at an object that is not a commit-ish, or make
the remote ref point at an object that is not a commit-ish.
statusHints
Show directions on how to proceed from the current state in the output
of git-status(1), in the template shown when writing commit messages in
git-commit(1), and in the help message shown by git-checkout(1) when
switching branch.
statusUoption
Advise to consider using the -u option to git-status(1) when the command
takes more than 2 seconds to enumerate untracked files.
commitBeforeMerge
Advice shown when git-merge(1) refuses to merge to avoid overwriting
local changes.
resolveConflict
Advice shown by various commands when conflicts prevent the operation
from being performed.
implicitIdentity
Advice on how to set your identity configuration when your information
is guessed from the system username and domain name.
detachedHead
Advice shown when you used git-checkout(1) to move to the detach HEAD
state, to instruct how to create a local branch after the fact.
amWorkDir
Advice that shows the location of the patch file when git-am(1) fails
to apply it.
rmHints
In case of failure in the output of git-rm(1), show directions on
how to proceed from the current state.
git -c advice.detachedHead=false checkout <refspec>
. – Interest