message: Cleanup variable assignments (FlatDb)
diff: @@ -354,10 +354,10 @@ export default class FileFlatDb implements BaseDb {
  l.debug(() => ['writeNewBranch', { branch, branchAt, entryIndex, key, prevValue, matchIndex, depth }]);
  const { keyAt, keyValue } = this.writeNewKey(key);
  - const newBranch = Buffer.alloc(BRANCH_SIZE);
  const keyIndex = ENTRY_SIZE * key.nibbles[matchIndex];
  const prevIndex = ENTRY_SIZE * prevValue.nibbles[matchIndex];
  - const newBranchAt = fs.fstatSync(this._fd).size;
  + let newBranchAt = fs.fstatSync(this._fd).size;
  + let newBranch = Buffer.alloc(BRANCH_SIZE);
  newBranch.set([Slot.LEAF], keyIndex);
  newBranch.writeUIntBE(keyAt, keyIndex + 1, UINT_SIZE);
  @@ -367,22 +367,20 @@ export default class FileFlatDb implements BaseDb {
  fs.writeSync(this._fd, branch, 0, BRANCH_SIZE, newBranchAt);
  this._cacheBranch(newBranchAt, newBranch);
  - let intermediateAt = newBranchAt;
  -
  for (let offset = 1; depth > 0; depth--, offset++) {
  - const intermediate = Buffer.alloc(BRANCH_SIZE);
  - const intermediateIndex = key.nibbles[matchIndex - offset] * ENTRY_SIZE;
  + const branchIndex = key.nibbles[matchIndex - offset] * ENTRY_SIZE;
  - intermediate.set([Slot.BRANCH], intermediateIndex);
  - intermediate.writeUIntBE(intermediateAt, intermediateIndex + 1, UINT_SIZE);
  - intermediateAt = fs.fstatSync(this._fd).size;
  + newBranch = Buffer.alloc(BRANCH_SIZE);
  + newBranch.set([Slot.BRANCH], branchIndex);
  + newBranch.writeUIntBE(newBranchAt, branchIndex + 1, UINT_SIZE);
  + newBranchAt += BRANCH_SIZE;
  - fs.writeSync(this._fd, intermediate, 0, BRANCH_SIZE, intermediateAt);
  - this._cacheBranch(intermediateAt, intermediate);
  + fs.writeSync(this._fd, newBranch, 0, BRANCH_SIZE, newBranchAt);
  + this._cacheBranch(newBranchAt, newBranch);
  }
  branch.set([Slot.BRANCH], entryIndex);
  - branch.writeUIntBE(intermediateAt, entryIndex + 1, UINT_SIZE);
  + branch.writeUIntBE(newBranchAt, entryIndex + 1, UINT_SIZE);
  fs.writeSync(this._fd, branch, entryIndex, ENTRY_SIZE, branchAt + entryIndex);
  return {
  