worktree: improve worktree setup message
When git-worktree creates a new worktree, it reports:
Enter "<path>" (identifier <tag>)
which misleadingly implies that it is setting <path> as the working
directory (as if "cd <path>" had been invoked), whereas it's actually
preparing the new worktree by creating its administrative files, setting
HEAD, and populating it. Make this more clear by instead saying:
Preparing "<path>" (identifier <tag>)
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>