+ # Read the manpage 'apt_preferences(5)', especially the chapter
+ # 'The Effect of APT Preferences' to understand the following logic
+ # and the difference between specific and general form
+ if is_array($packages) {
+ $packages_string = join($packages, ' ')
+ } else {
+ $packages_string = $packages
+ }
+
+ if $packages_string != '*' { # specific form
+ if ( $pin_release != '' and ( $origin != '' or $version != '' )) or
+ ( $version != '' and ( $pin_release != '' or $origin != '' )) {
+ fail('parameters release, origin, and version are mutually exclusive')
+ }
+ } else { # general form
+ if $version != '' {
+ fail('parameter version cannot be used in general form')
+ }
+ if ( $pin_release != '' and $origin != '' ) {
+ fail('parameters release and origin are mutually exclusive')
+ }
+ }