connect: factor out "looks like command line option" check

We reject hostnames that start with a dash because they may
be confused for command-line options. Let's factor out that
notion into a helper function, as we'll use it in more
places. And while it's simple now, it's not clear if some
systems might need more complex logic to handle all cases.

Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

path.c

@@ -1178,6 +1178,11 @@ int is_ntfs_dotgit(const char *name)
 		}
 }
 
+int looks_like_command_line_option(const char *str)
+{
+	return str && str[0] == '-';
+}
+
 char *xdg_config_home(const char *filename)
 {
 	const char *home, *config_home;