gitweb: quote commands properly when calling the shell

This eliminates the function git_cmd_str, which was used for composing
command lines, and adds a quote_command function, which quotes all of
its arguments (as in quote.c).

Signed-off-by: Lea Wiemann <LeWiemann@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -1500,9 +1500,13 @@ sub git_cmd {
 	return $GIT, '--git-dir='.$git_dir;
 }
 
-# returns path to the core git executable and the --git-dir parameter as string
-sub git_cmd_str {
-	return join(' ', git_cmd());
+# quote the given arguments for passing them to the shell
+# quote_command("command", "arg 1", "arg with ' and ! characters")
+# => "'command' 'arg 1' 'arg with '\'' and '\!' characters'"
+# Try to avoid using this function wherever possible.
+sub quote_command {
+	return join(' ',
+		    map( { my $a = $_; $a =~ s/(['!])/'\\$1'/g; "'$a'" } @_ ));
 }
 
 # get HEAD ref of given project as hash
@@ -4633,19 +4637,19 @@ sub git_snapshot {
 		$hash = git_get_head_hash($project);
 	}
 
-	my $git_command = git_cmd_str();
 	my $name = $project;
 	$name =~ s,([^/])/*\.git$,$1,;
 	$name = basename($name);
 	my $filename = to_utf8($name);
 	$name =~ s/\047/\047\\\047\047/g;
 	my $cmd;
 	$filename .= "-$hash$known_snapshot_formats{$format}{'suffix'}";
-	$cmd = "$git_command archive " .
-		"--format=$known_snapshot_formats{$format}{'format'} " .
-		"--prefix=\'$name\'/ $hash";
+	$cmd = quote_command(
+		git_cmd(), 'archive',
+		"--format=$known_snapshot_formats{$format}{'format'}",
+		"--prefix=$name/", $hash);
 	if (exists $known_snapshot_formats{$format}{'compressor'}) {
-		$cmd .= ' | ' . join ' ', @{$known_snapshot_formats{$format}{'compressor'}};
+		$cmd .= ' | ' . quote_command(@{$known_snapshot_formats{$format}{'compressor'}});
 	}
 
 	print $cgi->header(
@@ -4858,8 +4862,8 @@ sub git_object {
 	if ($hash || ($hash_base && !defined $file_name)) {
 		my $object_id = $hash || $hash_base;
 
-		my $git_command = git_cmd_str();
-		open my $fd, "-|", "$git_command cat-file -t $object_id 2>/dev/null"
+		open my $fd, "-|", quote_command(
+			git_cmd(), 'cat-file', '-t', $object_id) . ' 2> /dev/null'
 			or die_error('404 Not Found', "Object does not exist");
 		$type = <$fd>;
 		chomp $type;