Restructure client/ subdir. Add two different flavors of client.
The full featured birdc client code is in client/birdc/.
The new light client birtcl is in client/birdcl/.
Common sources of both clients are directly in client/.
Rework on-line auto-completion in client/command.c to conditionally turn off
ncurses-specific code.
Add lightweight client without libreadline and ncurses dependencies - birdcl.
The birdcl lacks support of history, on-line auto-completion and there
are different implementations of "more" functionality and help on '?' press.
New client operates in canonical terminal mode (apart from "more" display)
and therefore all commands have to be executed by a return key including help
commands (called by '?' character in the end of the line).
Apart from these limitations the interaction style should be the same as
for the full client - birdc.
Build of birdcl is always on (independent on --enable-client parameter).
Pull out routines for interacting with the server and interpreting
internal commands which are not dependent on libreadline and
ncurses libraries.
This is a preparation step for a new lightweight birdc client.
(the current version UNIX-specific) anyway, so it's useless to try splitting it
to sysdep and generic part. Instead of this, configure script decides (based on
system type and user's wish) what (if any) client should be built and what
autoconfiguration it requires. Also, the client provides its own die/bug/...
functions.
