D17 was reverted because it broke creating bundle for non-general delta repos.
The reason is the following: D17 made infinitepush extension override
changegroup.supportedoutgoingversion() function and discard '01' version.
For non-general delta repositories it resulted in broken hg bundle ...
command.
abort: repository does not support bundle version 01
This diff fixes it by not overriding supportedoutgoingversion(). Instead
getscratchbranchpart() has its own logic of selecting changegroup version.