Add more process functions and a motivating example (#73)

* make `Process.runProcess` and `Process.runProcess_` polymorphic over streams

* add `Process.setStdout` and `Process.useHandleClose` primitives

* create example of using a handle for the stdout of a process

examples/30-process-handlers.hell

@@ -0,0 +1,8 @@
+main = do
+  Temp.withSystemTempFile "example" \filePath handle -> do
+    Text.putStrLn $ Text.concat ["Created temp file ", filePath]
+    let proc = Process.setStdout (Process.useHandleClose handle) $ 
+         Process.proc "ls" ["-al"]
+    Process.runProcess_ proc
+    contents <- Text.readFile filePath
+    Text.putStrLn contents

src/Hell.hs

@@ -1250,8 +1250,7 @@ supportedLits =
       -- Process
       ("Process.proc", lit' $ \n xs -> proc (Text.unpack n) (map Text.unpack xs)),
       ("Process.setEnv", lit' $ Process.setEnv @() @() @() . map (bimap Text.unpack Text.unpack)),
-      ("Process.runProcess", lit' $ runProcess @IO @() @() @()),
-      ("Process.runProcess_", lit' $ runProcess_ @IO @() @() @()),
+
       -- Exit
       ("Exit.ExitSuccess", lit' Exit.ExitSuccess),
       ("Exit.ExitFailure", lit' Exit.ExitFailure),
@@ -1594,6 +1593,11 @@ polyLits =
                  -- Temp
                  "Temp.withSystemTempFile" temp_withSystemTempFile :: forall a. Text -> (Text -> IO.Handle -> IO a) -> IO a
                  "Temp.withSystemTempDirectory" temp_withSystemTempDirectory :: forall a. Text -> (Text -> IO a) -> IO a
+                 -- Process 
+                 "Process.runProcess" runProcess :: forall a b c. ProcessConfig a b c -> IO ExitCode
+                 "Process.runProcess_" runProcess_ :: forall a b c. ProcessConfig a b c -> IO ()
+                 "Process.setStdout" setStdout :: forall stdin stdout stdout' stderr. StreamSpec 'STOutput stdout' -> ProcessConfig stdin stdout stderr -> ProcessConfig stdin stdout' stderr
+                 "Process.useHandleClose" useHandleClose :: forall (a :: StreamType). IO.Handle -> StreamSpec a () 
                |]
      )