test-bundle2: also test the argument of the changegroup hook
We also track execution of the changegroup hook. The important information here
is to make sure the information that the transaction was processing a bundle2 is passed to
hook. This will let most hooks disable themselves while waiting for the hook
concluding bundle2 processing (the one we discovered to be not called for
pull in the previous changesets).
http://example.com/no/anchor, branches: (None, [])
http://example.com/an/anchor, branches: ('foo', [])
http://example.com/no/anchor/branches, branches: (None, ['foo'])
http://example.com/an/anchor/branches, branches: ('bar', ['foo'])
http://example.com/an/anchor/branches-None, branches: ('foo', [])
http://example.com/, branches: (None, [])
http://example.com/, branches: (None, [])
http://example.com/, branches: ('foo', [])