Simplify how we deal with empty source blobs.

src/SemanticDiff.hs

@@ -36,7 +36,7 @@ main = do
           blobs <- traverse readFile paths
           terms <- traverse (traverse parseBlob) blobs
           diff' <- runBothWith maybeDiff terms
-          return [(fromMaybe <$> (emptySourceBlob <$> paths) <*> blobs, diff')]
+          return [(fromMaybe . emptySourceBlob <$> paths <*> blobs, diff')]
         CommitDiff -> do
           blobPairs <- readFilesAtSHAs gitDir alternateObjectDirs filePaths (fromMaybe (toS nullOid) (fst shaRange)) (fromMaybe (toS nullOid) (snd shaRange))
           for blobPairs . uncurry $ \ path blobs -> do

test/IntegrationSpec.hs

@@ -123,7 +123,7 @@ testDiff renderer paths expectedOutput = do
     blobs <- traverse readFile paths
     terms <- traverse (traverse parseBlob) blobs
     Just diff' <- runBothWith maybeDiff terms
-    return (fromMaybe <$> (emptySourceBlob <$> paths) <*> blobs, diff')
+    return (fromMaybe . emptySourceBlob <$> paths <*> blobs, diff')
   let diffOutput = renderer blobs diff'
   let actual = Verbatim (stripWhitespace diffOutput)
   expected <- Verbatim . stripWhitespace <$> B.readFile expectedOutput