[PATCH 1/3] push: factor out the detached HEAD error message

With push.default set to upstream or simple, and a detached HEAD, git push prints the following error: $ git push fatal: You are not currently on a branch. To push the history leading to the current (detached HEAD) state now, use git push ram HEAD: This error is not unique to upstrea

[PATCH 1/3] push: factor out the detached HEAD error message

With push.default set to upstream or simple, and a detached HEAD, git push prints the following error: $ git push fatal: You are not currently on a branch. To push the history leading to the current (detached HEAD) state now, use git push ram HEAD: This error is not unique to upstrea