Accept second-wise time span as advertised in the help message.
Hello 2013.
Exit code should be $? >> 8 instead of $?.
Rebase on the parent commit for each modification.

This is required to keep previous merge commits intact.
Add real support for modifying multiple commits in the correct order.

A range form <committish1>..<committish2> is also supported.
Add -h/--help.
Use cherry-pick + commit --amend instead of filter-branch for speed.

Now it works blazingly faster because it doesn't mess with ancestor
commits any more.
Remove redundant reflog entries.