Understanding Binary Deltas within Packfile

[Luke Robison]

Is there any documentation of the contents of the binary delta datain a 
packfile, and how to interpret them?  I found 
https://github.com/git/git/blob/master/Documentation/technical/pack-format.txt 
documenting the packfile itself, but the "compressed delta data" seems 
largely undocumented.  The source code of 
https://github.com/git/git/blob/master/diff-delta.c is pretty dense.  
This is what I've got so for:

+-------------+
| Varint src_size
| Varint trg_size
| 1-byte inscnt
| N-bytes up to 16 bytes of trg_buf
|
| A series of Operations
|
+-------------

Any details on how to interpret the opcodes would be greatly appreciated.

Thanks,
Luke