[MERGE] Merge directive format 2, Bundle format 4

[Vincent Ladeuil]

Not a complete review, just a few remarks.

>>>>> "aaron" == Aaron Bentley <aaron.bentley at utoronto.ca> writes:

<snip/>

    aaron> === added file 'doc/developers/bundle-format4.txt'

Great ! Can you add a pointer to this file as comments in the relevant files ?

<snip/>

    aaron> === modified file 'bzrlib/errors.py'

We are nearly consistent in errors.py in defining exceptions
*without* a final 'Error' except for base classes to derive from.

Also, we are a bit less consistent in using a sentence explaining
the error as a format without duplicating the error name itself.

Compare:

IllegalMergeDirectivePayload: A merge directive contained something other than a patch or bundle

with

UnexpectedEndOfContainerError: Unexpected end of container stream

The 'sentence' thing needs an overhaul for the file, but can you
try harder for your new errors ?

    Vincent