Adding support for "plackup" and similar web server tools to git-instaweb

[Jakub Narebski <jnareb@gmail.com>]

I would like to add support for --httpd / instaweb.httpd = plackup
to git-instaweb.  'plackup'[1] is a command line utility to run 
PSGI[2][3] application (CGI application can be wrapped as such[4][5])
from the command line.  

Among others 'plackup' can use standalone HTTP::Server::PSGI server
(in Perl).  This means that one could use git-instaweb with 
--httpd=plackup even without permissions to install CGI scripts;
without admin rights (CPAN modules can be installed localy in one's
home directory using local::lib).


The problem is that contrary to other web servers that can be used by
git-instaweb, (namely apache2, lighttpd, mongoose and webrick), the
'plackup' utility is configured using command line options, and not
via configuration file (well, one can use configuration file, but it
depends on the web server run from plackup).

How should one go with adding support for such httpd?  My first attempt
was putting full command line into 'httpd' in resolve_full_httpd():

+       *plackup*)
+               # plackup is configured via command-line options
+               bind=
+               test x"$local" = xtrue && bind="--host=127.0.0.1"
+               httpd="$httpd --port=$port $bind --app=$fqgitdir/gitweb/app.psgi"
+               ;;

The default standalone web server used by plackup (HTTP::Server::PSGI)
does not have daemon mode, so we would have to do the same as for moongose
web server: set to background and save pid in pidfile in git-instaweb.

OTOH plackup prints information / logs to STDERR, so it would have to be
silenced or redirected to error_log.  Also plackup does not need to have
"$fqgitdir/gitweb/httpd.conf" passed as last argument, but it needs to
be passed PSGI wrapper for CGI (I'd rather not use httpd.conf, but rather
app.psgi or gitweb.psgi for that).


So how should one go with adding support for new web server to git-instaweb,
that is configured via command line options (--port, --host) and not via
config file?

[1] http://p3rl.org/plackup
[2] http://plackperl.org
[3] http://p3rl.org/PSGI
[4] http://p3rl.org/Plack::App::WrapCGI
[5] http://p3rl.org/CGI::Emulate::PSGI
[6] http://p3rl.org/Plack
-- 
Jakub Narebski
Poland