Summary:
To make "draft()" bounded and train users to hide unused commits manually,
change smartlog to "hide commits before <a static date>", instead of
"hide commits that are older than <a static time span>". Then we can
incrementally decrease the static date, and eventually show everything, and
force the user to think about what commits to keep or hide.
Reviewed By: singhsrb
Differential Revision: D13993584
fbshipit-source-id: 1a2b56f50d7f014a589f798cd2feaa6931e64fe3
