general-function.pl: Add a function to easily set defaults

This function can be used to set values in a hash if they have not been
set, yet.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

config/cfgroot/general-functions.pl

@@ -202,6 +202,17 @@ sub get_aliases
 	}
 }
 
+sub set_defaults($$) {
+	my $hash = shift;
+	my $defaults = shift;
+
+	foreach my $key (keys %$defaults) {
+		unless (defined($hash->{$key})) {
+			$hash->{$key} = $defaults->{$key};
+		}
+	}
+}
+
 sub readhash
 {
 	my $filename = $_[0];