view mercurial/__init__.py @ 21019:3dc09f831a2e

bundle2: lazy unbundle of part payload

The `unbundle` part gains a `read` method to retrieve payload content.
This method behaves as a python file-like read method.

The bundle-processing code is updated to make sure a part is fully consumed before
another one is extracted.

Test output changes because the debug output is even more interleaved now.