gitweb: Introduce common system-wide settings for convenience

Because of backward compatibility we cannot change gitweb to always
use /etc/gitweb.conf (i.e. even if gitweb_config.perl exists).  For
common system-wide settings we therefore need separate configuration
file: /etc/gitweb-common.conf.

Long description:

gitweb currently obtains configuration from the following sources:

  1. per-instance configuration file (default: gitweb_conf.perl)
  2. system-wide configuration file (default: /etc/gitweb.conf)

If per-instance configuration file exists, then system-wide
configuration is _not used at all_.  This is quite untypical and
suprising behavior.

Moreover it is different from way git itself treats /etc/git.conf.  It
reads in stuff from /etc/git.conf and then local repos can change or
override things as needed.  In fact this is quite beneficial, because
it gives site admins a simple and easy way to give an automatic hint
to a repo about things the admin would like.

On the other hand changing current behavior may lead to the situation,
where something in /etc/gitweb.conf may interfere with unintended
interaction in the local repository.  One solution would be to
_require_ to do explicit include; with read_config_file() it is now
easy, as described in gitweb/README (description introduced in this
commit).

But as J.H. noticed we cannot ask people to modify their per-instance
gitweb config file to include system-wide settings, nor we can require
them to do this.

Therefore, as proposed by Junio, for gitweb to have centralized config
elements while retaining backwards compatibility, introduce separate
common system-wide configuration file, by default /etc/gitweb-common.conf

Noticed-by: Drew Northup <drew.northup@maine.edu>
Helped-by: John 'Warthog9' Hawley <warthog9@kernel.org>
Inspired-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/gitweb/INSTALL b/gitweb/INSTALL
index c5236fee9d..f5efe7454c 100644
--- a/gitweb/INSTALL
+++ b/gitweb/INSTALL
@@ -231,7 +231,7 @@ Gitweb config file
 See also "Runtime gitweb configuration" section in README file
 for gitweb (in gitweb/README).
 
-- You can configure gitweb further using the gitweb configuration file;
+- You can configure gitweb further using the per-instance gitweb configuration file;
   by default this is a file named gitweb_config.perl in the same place as
   gitweb.cgi script. You can control the default place for the config file
   using the GITWEB_CONFIG build configuration variable, and you can set it
@@ -241,6 +241,17 @@ for gitweb (in gitweb/README).
   GITWEB_CONFIG_SYSTEM build configuration variable, and override it
   through the GITWEB_CONFIG_SYSTEM environment variable.
 
+  Note that if per-instance configuration file exists, then system-wide
+  configuration is _not used at all_.  This is quite untypical and suprising
+  behavior.  On the other hand changing current behavior would break backwards
+  compatibility and can lead to unexpected changes in gitweb behavior.
+  Therefore gitweb also looks for common system-wide configuration file,
+  normally /etc/gitweb-common.conf (set during build time using build time
+  configuration variable GITWEB_CONFIG_COMMON, set it at runtime using
+  environment variable with the same name).  Settings from per-instance or
+  system-wide configuration file override those from common system-wide
+  configuration file.
+
 - The gitweb config file is a fragment of perl code. You can set variables
   using "our $variable = value"; text from "#" character until the end
   of a line is ignored. See perlsyn(1) for details.