Make --pretend work

Distribution/Gentoo/PkgManager.hs

@@ -14,6 +14,7 @@ module Distribution.Gentoo.PkgManager
        , packageManagers
        , defaultPM
        , dummy
+       , setPretend
        , buildPkgs
        ) where
 
@@ -50,6 +51,13 @@ paludis = PM "paludis" "paludis" ["--install", "--preserve-world"
 dummy :: PkgManager
 dummy = PM "test PM" "echo" []
 
+-- All 3 PMs use --pretend to show what packages they would build;
+-- assume that they are all like this.
+setPretend    :: PkgManager -> PkgManager
+setPretend pm = pm { opts = pOpt : opts pm }
+    where
+      pOpt = "--pretend"
+
 buildPkgs    :: PkgManager -> [Package] -> IO ExitCode
 buildPkgs pm = system . buildCmd pm
 

Main.hs

@@ -106,7 +106,10 @@ argParser (fls, oth, []) = do unless (null oth)
            | otherwise        = DepCheck
 
     pmSpec = fmap unPM $ find isPM fls
-    pm = maybe (Just defaultPM) choosePM pmSpec
+    enablePretend = if hasFlag Pretend
+                    then setPretend
+                    else id
+    pm = fmap enablePretend $ maybe (Just defaultPM) choosePM pmSpec
 
     choosePM str = find ((==) str' . name) packageManagers
         where
@@ -169,7 +172,7 @@ options =
       $ "Use package manager PM, where PM can be one of:\n"
             ++ pmList ++ defPM
     , Option ['p']      ["pretend"]         (NoArg Pretend)
-      "Only pretend to build packages, currently ignored."
+      "Only pretend to build packages."
     , Option ['v']      ["version"]         (NoArg Version)
       "Version information."
     , Option ['h', '?'] ["help"]            (NoArg Help)