amend auto-save commits if the changes are "small"

[jdleesmiller]

It may make sense to amend changes if they were too close (time-wise or if changes are minimal). This could yield a cleaner commit history.

We don't want to lose author information, but if all of the edits are from one author, we don't lose much by amending. On the other hand, we have to be careful not to amend a commit that someone else has pulled, because that would break the history. This may be more trouble than it's worth, but it's one to think about.