gitweb: fallback to system-wide config file if default config does not exist

From a distribution point of view, configuration files for applications
should reside in /etc/.  On the other hand it's convenient for multiple
instances of gitweb (e.g. virtual web servers on a single machine) to have
a per-instance configuration file, just as gitweb currently supports
through the file gitweb_config.perl next to the cgi.

To support both at runtime, this commit introduces GITWEB_CONFIG_SYSTEM as
a system-wide configuration file which will be used as a fallback if the
config file sprecified throug GITWEB_CONFIG does not exist.

See also
 http://bugs.debian.org/450592

Signed-off-by: Gerrit Pape <pape@smarden.org>
Acked-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -189,6 +189,7 @@ ETC_GITCONFIG = $(sysconfdir)/gitconfig
 
 # default configuration for gitweb
 GITWEB_CONFIG = gitweb_config.perl
+GITWEB_CONFIG_SYSTEM = /etc/gitweb.conf
 GITWEB_HOME_LINK_STR = projects
 GITWEB_SITENAME =
 GITWEB_PROJECTROOT = /pub/git

gitweb/INSTALL

@@ -95,7 +95,11 @@ for gitweb (in gitweb/README).
   by default it is file named gitweb_config.perl in the same place as
   gitweb.cgi script. You can control default place for config file
   using GITWEB_CONFIG build configuration variable, and you can set it
-  using GITWEB_CONFIG environmental variable.
+  using GITWEB_CONFIG environmental variable. If this file does not
+  exist, gitweb looks for a system-wide configuration file, normally
+  /etc/gitweb.conf. You can change the default using the
+  GITWEB_CONFIG_SYSTEM build configuration variable, and override it
+  through GITWEB_CONFIG_SYSTEM environmental variable.
 
 - Gitweb config file is [fragment] of perl code. You can set variables
   using "our $variable = value"; text from "#" character until the end

gitweb/README

@@ -100,13 +100,20 @@ You can specify the following configuration variables when building GIT:
    is set when gitweb.cgi is executed, then the file specified in the
    environment variable will be loaded instead of the file specified
    when gitweb.cgi was created.  [Default: gitweb_config.perl]
+ * GITWEB_CONFIG_SYSTEM
+   This Perl file will be loaded using 'do' as a fallback if GITWEB_CONFIG
+   does not exist.  If the environment variable GITWEB_CONFIG_SYSTEM is set
+   when gitweb.cgi is executed, then the file specified in the environment
+   variable will be loaded instead of the file specified when gitweb.cgi was
+   created.  [Default: /etc/gitweb.conf]
 
 
 Runtime gitweb configuration
 ----------------------------
 
 You can adjust gitweb behaviour using the file specified in `GITWEB_CONFIG`
-(defaults to 'gitweb_config.perl' in the same directory as the CGI).
+(defaults to 'gitweb_config.perl' in the same directory as the CGI), and
+as a fallback `GITWEB_CONFIG_SYSTEM` (defaults to /etc/gitweb.conf).
 The most notable thing that is not configurable at compile time are the
 optional features, stored in the '%features' variable.
 

gitweb/gitweb.perl

@@ -369,7 +369,12 @@ sub filter_snapshot_fmts {
 }
 
 our $GITWEB_CONFIG = $ENV{'GITWEB_CONFIG'} || "++GITWEB_CONFIG++";
-do $GITWEB_CONFIG if -e $GITWEB_CONFIG;
+if (-e $GITWEB_CONFIG) {
+	do $GITWEB_CONFIG;
+} else {
+	our $GITWEB_CONFIG_SYSTEM = $ENV{'GITWEB_CONFIG_SYSTEM'} || "++GITWEB_CONFIG_SYSTEM++";
+	do $GITWEB_CONFIG_SYSTEM if -e $GITWEB_CONFIG_SYSTEM;
+}
 
 # version of the core git binary
 our $git_version = qx($GIT --version) =~ m/git version (.*)$/ ? $1 : "unknown";