As discussed in the question about What kind of stitch makes up t-shirt seams on commercial grade clothing? we can now identify the overlock stitch. A cursory look at the Wiki for that stitch shows that is way too complicated (or at least seems that way) for someone to do by hand.
When repairing a seam on clothing what would be a good stitch to consider that can be done by hand? I mostly use blanket stitches. However, those perform poorly under stress and you can see all sorts of gaps.