Add a truncatePatch function

src/DiffOutput.hs

@@ -22,6 +22,12 @@ printDiff parser arguments sources = case format arguments of
   Patch -> diffFiles parser P.patch sources
   JSON -> diffFiles parser J.json sources
 
+truncatedDiff :: DiffArguments -> Both SourceBlob -> IO Text
+truncatedDiff arguments sources = case format arguments of
+  Split -> return ""
+  Patch -> return $ P.truncatePatch arguments sources
+  JSON -> return "{}"
+
 printDiff' :: Parser -> DiffArguments -> Both SourceBlob -> IO ()
 printDiff' parser arguments sources = case format arguments of
   Split -> put (output arguments) =<< diffFiles parser split sources

src/Renderer/Patch.hs

@@ -1,7 +1,8 @@
 module Renderer.Patch (
   patch,
   hunks,
-  Hunk(..)
+  Hunk(..),
+  truncatePatch
 ) where
 
 import Alignment
@@ -22,6 +23,10 @@ import Data.Maybe
 import Data.Monoid
 import Data.Text (pack, Text)
 
+-- | Render a timed out file as a truncated diff.
+truncatePatch :: DiffArguments -> Both SourceBlob -> Text
+truncatePatch arguments blobs = pack $ header blobs ++ "#timed_out\nTruncating diff: timeout reached.\n"
+
 -- | Render a diff in the traditional patch format.
 patch :: Renderer a Text
 patch diff blobs = pack $ case getLast (foldMap (Last . Just) string) of