fixup! Add --install-cabal option for stack setup.

src/Stack/Setup.hs

@@ -494,7 +494,7 @@ ensureCompiler sopts = do
         unless needLocal $ do
             $logWarn "Trying to change a Cabal library on a GHC not installed by stack."
             $logWarn "This may fail, caveat emptor!"
-        upgradeCabal menv wc (fromJust cabalVersion)
+        forM_ cabalVersion (upgradeCabal menv wc)
 
     case mtools of
         Just (Just (ToolGhcjs cv), _) -> ensureGhcjsBooted menv cv (soptsInstallIfMissing sopts)
@@ -660,10 +660,10 @@ upgradeCabal menv wc cabalVersion = do
             m <- unpackPackageIdents menv tmpdir Nothing (Map.singleton ident Nothing)
 
             compilerPath <- join $ findExecutable menv (compilerExeName wc)
-            newestDir <- parseRelDir $ versionString version
+            versionDir <- parseRelDir $ versionString version
             let installRoot = toFilePath $ parent (parent compilerPath)
                                        </> $(mkRelDir "new-cabal")
-                                       </> newestDir
+                                       </> versionDir
             dir <-
                 case Map.lookup ident m of
                     Nothing -> error "upgradeCabal: Invariant violated, dir missing"

src/Stack/Types/Version.hs

@@ -65,7 +65,7 @@ instance Exception VersionParseFail
 instance Show VersionParseFail where
     show (VersionParseFail bs) = "Invalid version: " ++ show bs
 
--- | A package version or the latest.
+-- | A Package upgrade; Latest or a specific version.
 data UpgradeTo = Specific Version | Latest deriving (Show)
 
 -- | A package version.