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>

builtin/worktree.c

@@ -245,7 +245,7 @@ static int add_worktree(const char *path, const char **child_argv)
 	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
 	write_file(sb.buf, 1, "../..\n");
 
-	fprintf_ln(stderr, _("Enter %s (identifier %s)"), path, name);
+	fprintf_ln(stderr, _("Preparing %s (identifier %s)"), path, name);
 
 	setenv("GIT_CHECKOUT_NEW_WORKTREE", "1", 1);
 	setenv(GIT_DIR_ENVIRONMENT, sb_git.buf, 1);