writebundle: add a compression argument for the bundle2 case...
writebundle: add a compression argument for the bundle2 case
Bundle2 compression is more complex than the bundle1 one. Therefore it
is handled by the bundler itself. Moreover, on-disk bundle2 will
probably have a large number of flavors so simply adding a new "format"
for it does not seems the way to go.
This will be used in the next changeset to compress bundle2 strip backup.