feat(merge-lane)!: change no-snap to avoid fast-forward

[davidfirst]

Until now, in case lane-b is merged into lane-a and a component (e.g. comp-a) is ahead in lane-b, we simply updated lane-a with the new snap of lane-b. (this behavior is similar to the "fast-forward" in Git).
This was true regardless of --no-snap flag. The --no-snap flag was only for cases when comp-a is diverged in history and no conflicts found, which was auto-snapping the component and saving two parents, the head of lane-a and the head of lane-b.

In come cases, the end result of such a merge is not desirable. Some changes might be done to this comp-a in lane-b which I would like to investigate and test before I decide to get them in lane-a. Although comp-a wasn't changed/snapped in my lane-a, still, I prefer to get the changes of comp-a as modified, so then bit diff will show the new changes I'm getting and then I can decide later to snap these changes.
This PR makes this possible by using the --no-snap flag. In practice, it considers this state of target-ahead (lane-b) as diverged, which, as a result - doesn't update lane-a, only the component-files and the unmerged files with the heads data.

A new flag --no-auto-snap was introduced to keep the previous behavior of --no-snap in case users need them.