[RFC/PATCH] gitweb: Fail early

[Jakub Narebski <jnareb@gmail.com>]

Return HTTP 500 Internal Server Error if $GIT is not defined (which
would cause Perl error), or if "$GIT --version" failed to run.  This
should not happen often, but I think this change would make diagnosing
misconfiguration easier.
---
Is "git version" in 'git --version' output ensured? How did other git
implementations and ports (like msysGit and jgit) output of --version
looks like?

Does it make sense to check whether output matches, and if it doesn't
match assume that $GIT points to something other, perhaps some other
git like GIT Interactive Tools or something?

Does it makes sense to try various other checks to make error message
more detailed like $GIT is not found, or is not executable?

diff --git i/gitweb/gitweb.perl w/gitweb/gitweb.perl
index 05702e4..0cb53ca 100755
--- i/gitweb/gitweb.perl
+++ w/gitweb/gitweb.perl
@@ -471,7 +471,13 @@ if (-e $GITWEB_CONFIG) {
 }
 
 # version of the core git binary
+if (!defined $GIT) {
+	die_error(500, "Undefined path to git binary");
+}
 our $git_version = qx("$GIT" --version) =~ m/git version (.*)$/ ? $1 : "unknown";
+if ($?) {
+	die_error(500, "Error calling '$GIT --version': $?");
+}
 
 $projects_list ||= $projectroot;