wireprotov2: re-add tuple around `bundle2` check
I stumbled upon this while looking for the current (v1) `capable` method. It
looks like
9c2c77c73f23 accidentally removed the comma, turning the tuple into
a simple parenthesis expression.
This has not been detected since wireproto2 is not in use AFAIK.
Differential Revision: https://phab.mercurial-scm.org/D9518
upgrade: gather code about requirement checking together
They just moved in the same file, now they are grouped together and documented.
Differential Revision: https://phab.mercurial-scm.org/D9486
upgrade: extract the checking of target requirements change
This logic is fairly independant, lets move it out of the main function.
Differential Revision: https://phab.mercurial-scm.org/D9485