[RFC] Splitting gitweb and build-time configuration variables

I am planning on picking up and resubmitting "splitting gitweb" series, which was created by Pavan as a prerequisite for adding write and admin support to gitweb ("Splitting gitweb and developing write functionalities (Integrated web client for git)" GSoC 2010 project).

There is a question what to do about gitweb configuration variables which are set during build time, like e.g.:

  # URI of stylesheets
  our @stylesheets = ("++GITWEB_CSS++");

or

  # core git executable to use
  # this can just be "git" if your webserver has a sensible PATH
  our $GIT = "++GIT_BINDIR++/git";

I think it was agreed that _setting_ these variables would be left in gitweb.perl, to have one single place which gathers all such variables, and to have gitweb/Makefile to munge (transform) only a single file.

So those variables would be _declared_ in appropriate gitweb module (Gitweb::Git aka Gitweb::Command, Gitweb::Config, Gitweb::Util etc.) but would be _defined_ (set to value) in gitweb.perl. The final goal is to have gitweb.perl consist only of loading modules, build-time configuration, and starting gitweb (calling run() or similarly named subroutine or method).

The question is where *description* of those build time configuration variables should be (see the above examples). Should it be:

1. Description of build-time configuration variable is in the module
   that defines it, and each block of variables coming from the same
   module would have notice where one can find description of those
   variables, like in original patches by Pavan, e.g.:

     # Only configuration variables with build-time overridable
     # defaults are listed below. The complete set of variables
     # with their descriptions is listed in Gitweb::Config.

or

2. Description of build-time configuration variables is in gitweb.perl,
   and in each module there is comment that full description of those
   variables can be found there, e.g. (proposal):

     # Values of those variables are set during build time in 
     # gitweb/gitweb.perl (main script).  You can find their description
     # there.

or perhaps

3. Duplicate description of those variables, to have it both in
   appropriate module and in gitweb.perl

What do you think about it?

Jakub Narebski wrote:

[...]

[...]

With #2, a person reading the Makefile can grep for some particular substitution (++GITWEB_PROJECTROOT++) and quickly find the name and description of the variable it is used for. If there were a 1:1 correspondence between the variables in gitweb.perl and the Makefile, I would even suggest moving the description to the Makefile.

In practice, I suspect the run-time configuration is more important to people. That is already fairly well documented in gitweb/README.

Just my two cents, Jonathan

On Wed, 18 Aug 2010, Jonathan Nieder wrote:

There is a bit of difference between Perl variables in gitweb.perl and make build-time variables in gitweb/Makefile, namely:

  our $GIT = "++GIT_BINDIR++/git";

  our $site_name = "++GITWEB_SITENAME++"
                 || ($ENV{'SERVER_NAME'} || "Untitled") . " Git";

  our @stylesheets = ("++GITWEB_CSS++");

  our @git_base_url_list = grep { $_ ne '' } ("++GITWEB_BASE_URL++");

  our $GITWEB_CONFIG = $ENV{'GITWEB_CONFIG'} || "++GITWEB_CONFIG++";
  our $GITWEB_CONFIG_SYSTEM = $ENV{'GITWEB_CONFIG_SYSTEM'}
                            || "++GITWEB_CONFIG_SYSTEM++";

Perl variables can be overriden in run-time configuration (testsuite uses this to test _source_ version i.e. gitweb.perl rather than generated gitweb.cgi), so they have to be described anyway.

I think that adding description of make variables to gitweb/Makefile, similar to what main Makefile does, would be a good idea, though I don't like that it leads to some duplication.

Build-time configuration is also described in gitweb/README, in more detail.