git worktree add prints to stdout

[Karen Arutyunov]

Hello,

The 'git worktree add' command prints to both standard streams. So in 
the following example the first line is printed to stderr and the second 
to stdout.

$ git worktree add ../pub build2-control
Preparing ../pub (identifier pub)
HEAD is now at b03ea86 Update

This looks like a bug, as, for example, the checkout command prints 
'HEAD is now at...' message to stderr.

Best regards,
Karen