From d4417fba9c5db5fbbbcaac4315c52c0a6c1af652 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <p.giarrusso@gmail.com>
Date: Sat, 6 Aug 2016 13:48:28 +0200
Subject: [PATCH 1/2] Only use gtar on OpenBSD for xz archives (#2283)

Since OpenBSD's tar does not support xz, use only `gtar` there. Stick to
`tar` elsewhere.

The UX is not perfect but it's already useful.
---
 src/Stack/Setup.hs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Stack/Setup.hs b/src/Stack/Setup.hs
index d70b7d58be..76555d2188 100644
--- a/src/Stack/Setup.hs
+++ b/src/Stack/Setup.hs
@@ -819,10 +819,16 @@ installGHCPosix version _ archiveFile archiveType destDir = do
             TarBz2 -> return "bzip2"
             TarGz -> return "gzip"
             SevenZ -> error "Don't know how to deal with .7z files on non-Windows"
+    -- Slight hack: OpenBSD's tar doesn't support xz.
+    -- https://github.com/commercialhaskell/stack/issues/2283#issuecomment-237980986
+    let tarDep =
+          case (platform, archiveType) of
+            (Platform _ Cabal.OpenBSD, TarXz) -> checkDependency "gtar"
+            _ -> checkDependency "tar"
     (zipTool, makeTool, tarTool) <- checkDependencies $ (,,)
         <$> checkDependency zipTool'
         <*> (checkDependency "gmake" <|> checkDependency "make")
-        <*> checkDependency "tar"
+        <*> tarDep
 
     $logDebug $ "ziptool: " <> T.pack zipTool
     $logDebug $ "make: " <> T.pack makeTool

From 0ae54114de8c5427858c5997b64e6b7365244962 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <p.giarrusso@gmail.com>
Date: Mon, 8 Aug 2016 18:48:16 +0200
Subject: [PATCH 2/2] stack setup: Specify decompressor to tar

This supports non-GNU tar programs that do not decompress archives
automatically, such as the OpenBSD one.
---
 src/Stack/Setup.hs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/Stack/Setup.hs b/src/Stack/Setup.hs
index 76555d2188..0b8ad69faa 100644
--- a/src/Stack/Setup.hs
+++ b/src/Stack/Setup.hs
@@ -813,11 +813,11 @@ installGHCPosix version _ archiveFile archiveType destDir = do
     menv0 <- getMinimalEnvOverride
     menv <- mkEnvOverride platform (removeHaskellEnvVars (unEnvOverride menv0))
     $logDebug $ "menv = " <> T.pack (show (unEnvOverride menv))
-    zipTool' <-
+    (zipTool', compOpt) <-
         case archiveType of
-            TarXz -> return "xz"
-            TarBz2 -> return "bzip2"
-            TarGz -> return "gzip"
+            TarXz -> return ("xz", 'J')
+            TarBz2 -> return ("bzip2", 'j')
+            TarGz -> return ("gzip", 'z')
             SevenZ -> error "Don't know how to deal with .7z files on non-Windows"
     -- Slight hack: OpenBSD's tar doesn't support xz.
     -- https://github.com/commercialhaskell/stack/issues/2283#issuecomment-237980986
@@ -842,7 +842,7 @@ installGHCPosix version _ archiveFile archiveType destDir = do
 
         $logSticky $ T.concat ["Unpacking GHC into ", T.pack . toFilePath $ root, " ..."]
         $logDebug $ "Unpacking " <> T.pack (toFilePath archiveFile)
-        readInNull root tarTool menv ["xf", toFilePath archiveFile] Nothing
+        readInNull root tarTool menv [compOpt : "xf", toFilePath archiveFile] Nothing
 
         $logSticky "Configuring GHC ..."
         readInNull dir (toFilePath $ dir </> $(mkRelFile "configure"))