This will make for a shorter storage and help use to write faster code in simple
case. This change already provided a speed boost for copy tracing.
For example here is combined time of running copies tracing on a 6989 pairs of
revision on the pypy repos:
after: 631s - 18%
This also has a very positive impact on changelog size. For example here are the
number for the 00changelog.d file of pypy.
before: 30449712 Bytes
after: 24973718 Bytes - 18%
This give an overall quite acceptable overhead for storing copies into the
sidedata: 24973718 Bytes + 7%