work around broken getEnvironment on Android in the most important place: git annex init

This resulted in a lot of user complains that git annex init had git
telling them they needed to run git config --global user.email .. which
didn't work because even HOME was not passed into git.

Annex/Branch.hs

@@ -5,6 +5,8 @@
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
+{-# LANGUAGE CPP #-}
+
 module Annex.Branch (
 	fullname,
 	name,
@@ -22,7 +24,7 @@ module Annex.Branch (
 ) where
 
 import qualified Data.ByteString.Lazy.Char8 as L
-import System.Environment
+import System.Posix.Env
 
 import Common.Annex
 import Annex.BranchState
@@ -285,7 +287,17 @@ withIndex' :: Bool -> Annex a -> Annex a
 withIndex' bootstrapping a = do
 	f <- fromRepo gitAnnexIndex
 	g <- gitRepo
+#ifdef WITH_ANDROID
+	{- Work around for weird getEnvironment breakage on Android. See
+	 - https://github.com/neurocyte/ghc-android/issues/7
+	 - Instead, use getEnv to get some key environment variables that
+	 - git expects to have. -}
+	let keyenv = words "USER PATH GIT_EXEC_PATH HOSTNAME HOME"
+	let getEnvPair k = maybe Nothing (\v -> Just (k, v)) <$> getEnv k
+	e <- liftIO $ catMaybes <$> forM keyenv getEnvPair
+#else
 	e <- liftIO getEnvironment
+#endif
 	let g' = g { gitEnv = Just $ ("GIT_INDEX_FILE", f):e }
 
 	Annex.changeState $ \s -> s { Annex.repo = g' }

doc/design/assistant/android.mdwn

@@ -33,3 +33,5 @@ file modes, etc.
 * Make git stop complaining that "warning: no threads uspport, ignoring --threads"
 * git does not support http remotes. To fix, need to port libcurl and
   allow git to link to it.
+* getEnvironment is broken on Android <https://github.com/neurocyte/ghc-android/issues/7>
+  and a few places use it.