scripts/feeds: add src-dummy method

The src-dummy method does not actually obtain any feed, but it can be used
to insert addtional entries into the opkg distfeeds.conf. This is useful to
make package feeds available to users without requiring the corresponding
source feeds to be available during build.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

scripts/feeds

@@ -59,7 +59,8 @@ sub parse_config() {
 		my $valid = 1;
 		$line[0] =~ /^src-[\w-]+$/ or $valid = 0;
 		$line[1] =~ /^\w+$/ or $valid = 0;
-		@src = split /\s+/, $line[2];
+		@src = split /\s+/, ($line[2] or '');
+		@src = ('') if @src == 0;
 		$valid or die "Syntax error in feeds.conf, line: $line\n";
 
 		$name{$line[1]} and die "Duplicate feed name '$line[1]', line: $line\n";
@@ -127,6 +128,10 @@ my %update_method = (
 		'init'		=> "ln -s '%s' '%s'",
 		'update'	=> "",
 		'revision'	=> "echo -n 'local'"},
+	'src-dummy' => {
+		'init'		=> "true '%s' && mkdir '%s'",
+		'update'	=> "",
+		'revision'	=> "echo -n 'dummy'"},
 	'src-git' => {
 		'init'          => "git clone --depth 1 '%s' '%s'",
 		'init_branch'   => "git clone --depth 1 --branch '%s' '%s' '%s'",