Huge win, compressing a window of delta runs as a unit

["Jon Smirl" <jonsmirl@gmail.com>]

Shawn put together a new version of his import utility that packs all
of the deltas from a run into a single blob instead of one blob per
delta. The idea is to put 10 or more deltas into each delta entry
instead of one. The index format would map the 10 sha1's to a single
packed delta entry which would be expanded when needed. Note that you
probably needed multiple entries out of the delta pack to generate the
revision you were looking for so this is no real loss on extraction.

I ran it overnight on mozcvs. If his delta pack code is correct this
is a huge win.

One entry per delta -  845,42,0150
Packed deltas - 295,018,474
65% smaller

The effect of packing the deltas is to totally eliminate many of the
redundant zlib dictionaries.

This is without using a zlib dictionary which gains another 4% form a
4KB dictionary.

-- 
Jon Smirl
jonsmirl@gmail.com