Revert "LocalStore::addToStore(srcPath): Handle the flat case"

This reverts commit a2c2702. See
addToStoreSlow(), we don't need to handle this case efficiently
anymore. In fact, we can almost remove the method/hashAlgo arguments
since the non-recursive and/or non-SHA256 are almost not used anymore.

src/libstore/local-store.cc

@@ -1097,13 +1097,16 @@ StorePath LocalStore::addToStore(const string & name, const Path & _srcPath,
 {
     Path srcPath(absPath(_srcPath));
 
+    if (method != FileIngestionMethod::Recursive)
+        return addToStoreFromDump(readFile(srcPath), name, method, hashAlgo, repair);
+
     /* For computing the NAR hash. */
     auto sha256Sink = std::make_unique<HashSink>(htSHA256);
 
     /* For computing the store path. In recursive SHA-256 mode, this
        is the same as the NAR hash, so no need to do it again. */
     std::unique_ptr<HashSink> hashSink =
-        method == FileIngestionMethod::Recursive && hashAlgo == htSHA256
+        hashAlgo == htSHA256
         ? nullptr
         : std::make_unique<HashSink>(hashAlgo);
 
@@ -1136,10 +1139,7 @@ StorePath LocalStore::addToStore(const string & name, const Path & _srcPath,
             if (!inMemory) sink(buf, len);
         });
 
-        if (method == FileIngestionMethod::Recursive)
-            dumpPath(srcPath, sink2, filter);
-        else
-            readFile(srcPath, sink2);
+        dumpPath(srcPath, sink2, filter);
     });
 
     std::unique_ptr<AutoDelete> delTempDir;
@@ -1155,10 +1155,7 @@ StorePath LocalStore::addToStore(const string & name, const Path & _srcPath,
         delTempDir = std::make_unique<AutoDelete>(tempDir);
         tempPath = tempDir + "/x";
 
-        if (method == FileIngestionMethod::Recursive)
-            restorePath(tempPath, *source);
-        else
-            writeFile(tempPath, *source);
+        restorePath(tempPath, *source);
 
     } catch (EndOfFile &) {
         if (!inMemory) throw;
@@ -1191,10 +1188,7 @@ StorePath LocalStore::addToStore(const string & name, const Path & _srcPath,
             if (inMemory) {
                 /* Restore from the NAR in memory. */
                 StringSource source(nar);
-                if (method == FileIngestionMethod::Recursive)
-                    restorePath(realPath, source);
-                else
-                    writeFile(realPath, source);
+                restorePath(realPath, source);
             } else {
                 /* Move the temporary path we restored above. */
                 if (rename(tempPath.c_str(), realPath.c_str()))