enable vty xml dumping to stdout

Allow dumping the VTY XML reference (for generating manuals) to a normal FILE*
stream instead of a vty output buffer.

We currently generate the VTY reference by starting the client program,
connecting to the VTY telnet and dumping the reference. That is weirdly
convoluted, especially since there has to be a valid config file that
successfully starts up a minimal set of external links before the reference can
be generated. IMO we should have dumped the XML reference to stdout from the
start, and never to a VTY session.

With this patch, it is trivial to generate the XML VTY reference by a
commandline switch. The client program will set up the entire VTY, and
immediately after parsing the cmdline options but before parsing a config file,
just dumps the reference and doesn't even start establishing local ports. That
would allow generating the XML reference on the fly during the build process of
the manuals, without the need of a docker container or somesuch.

A first implementation of such a commandline switch is `osmo-bsc -X`, added in
I316efedb2c1652791434ecf14a1e261367cd2fb7

This patch jumps through a bit of a hoop to still allow dumping to a VTY buffer
without code dup, to still allow dumping the XML reference through telnet VTY,
until all our programs have implemented an -X switch (TM).

Change-Id: Ic74bbdb6dc5ea05f03c791cc70184861e39cd492

1 files changed, 2 insertions, 0 deletions

diff --git a/include/osmocom/vty/command.h b/include/osmocom/vty/command.h
index d63dbdef..88490f79 100644
--- a/include/osmocom/vty/command.h
+++ b/include/osmocom/vty/command.h
@@ -401,4 +401,6 @@ void print_version(int print_copyright);
 
 extern void *tall_vty_cmd_ctx;
 
+int vty_dump_xml_ref(FILE *stream);
+
 /*! @} */