gitweb: Add git_project_index for generating index.aux
Add git_project_index, which generates index.aux file that can be used
as a source of projects list, instead of generating projects list from
a directory. Using file as a source of projects list allows for some
projects to be not present in gitweb main (project_list) page, and/or
correct project owner info. And is probably faster.
Additionally it can be used to get the list of all available repositories
for scripts (in easily parseable form).
Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>