enforcesinglehead-test: add the expected node output next to the error this make it simpler to validate that the test is correct. Differential Revision: https://phab.mercurial-scm.org/D10545

revlog: code for `revlogv0` in its own module This code is mostly unused compatiblity code. Yet it take a prohiminent place in the `revlog.py` module. That module is already quite big, so we move all that code in a dedicated module. Differential Revision: https://phab.mercurial-scm.org/D10511

revlog: have an explicit "pack_header" method Having to pass the version header when retrieving the binary version of every single entry is a bit silly. So we extract that special logic in its own method. This also prepare the move to newer revlog format, not storing the header within an actual entry… Differential Revision: https://phab.mercurial-scm.org/D10510

revlog: remove the revlogio class The class only contains a single `parseindex` method. Lets just make it a function and remove the `revlogio` class. It served us well but became thinner and thinner overtime. Differential Revision: https://phab.mercurial-scm.org/D10509

revlog: fix some comment style They displease check-code. Differential Revision: https://phab.mercurial-scm.org/D10542

revlog: add a `entry_binary` method on index The revlog index is already responsible for unpacking the binary entry, it would be simpler to make it responsible for packing them. In practice the C version of the index is already doing this internally. We introduce a "entry_binary" method that return the binary version of an existing revision. The method currently need to also take the revlog header to deal with the "first revision" special case. We will introduce further refactor in a later changeset to split that logic out. Differential Revision: https://phab.mercurial-scm.org/D10508

template: make an explicit closure for formatting entry in peerurls This is about to be become significantly more complicated as `ui.path[x]` will become a list. Differential Revision: https://phab.mercurial-scm.org/D10443

template: use `list_paths` in `peerurls` Using common code will make it simpler to update the logic behind the path definition and storage. Differential Revision: https://phab.mercurial-scm.org/D10442

paths: use `list_paths` in `hg paths` Using common code will make it simpler to update the logic behind the path definition and storage. Differential Revision: https://phab.mercurial-scm.org/D10441

urlutil: introduce a new `list_paths` function This function will be useful for command and template that wants to display path related information. Differential Revision: https://phab.mercurial-scm.org/D10440