Reduce the number of scope expansions during overlapped file detection in Version::GetOverlappingInputs

[caelumable]

if (begin != nullptr && user_cmp->Compare(file_start, user_begin) < 0) {
  user_begin = file_start;
  inputs->clear();
  i = 0;
 } else if (end != nullptr &&
           user_cmp->Compare(file_limit, user_end) > 0) {
  user_end = file_limit;
  inputs->clear();
  i = 0;
}

If the range of user_begin and user_end is [c, d] while the range of file_start and file_limit is [a, g], this would result in two scope expansions: first expanding user_begin and user_end to [a, d], and then further expanding them to [a, g], thereby increasing the number of loop iterations.

Removing this else clause would allow completing the scope expansion in a single step by directly adjusting user_begin and user_end to [a, g].