tests: merge two tests about split changesets Because the removed test case is essentially already included in the succeeding one, the tests are merged by removing the first.

evolve: support successors of ancestor of orphan with multiple roots The previous code checked that the set of successors has a single root. However, there’s no reason to require that in general. Example: o 6 | o 5 |\ | o 4 | | o | 3 |/ | * 2 | | | x 1 |/ o 0 1 is obsoleted by 3, 4 and 6. We are considering the case when 2 gets evolved. The roots are [3, 4] and the heads are [6]. Before the change, the user was asked which destination to choose, but there was only one choice (6). After the change, 6 is chosen as the destination.

evolve: support ancestor of orphan split with unrelated changeset in between This is done by searching for roots and heads within the range delimited on both sides by the target revs instead of just within the target revs. Example: o 5 | o 4 | o 3 | | * 2 | | | x 1 |/ o 0 1 is obsoleted by 3 and 5. We are considering the case when 2 gets evolved. Before the change, both roots and heads were [3, 5]. The user was offered a choice between 3 and 5 as the destination. After the change, roots are [3] and heads are [5]. 5 is chosen as the destination.

exchange: deal with empty obscommon The case can happen, we better support it.

topic: compat with tr.changes[b'phases'], it's now a list

topic: fix compatibility issues caused because of change in transaction API In 36f08ae87ef687be53a59bd87376bcfbe4479205 in core mercurial, `_validator` attribute to transaction class was removed and a dict was introduced. It added a `addvalidator()` function to transaction class which can be used to register multiple validator callbacks. This updates the code to use `addvalidator()` when `_validator` attribute is not present.

obsexchange: fallback to simpler request for dumb http server If the http server cannot accept many arguments, avoid sending too large requests (at the cost of more data exchanged). A better solution would be to aggregate contiguous range, but this is a question for later.

obsexchange: swap the 'common' and 'missing' clause

obsdiscovery: avoid considering locally hidden changeset This looks like a dubious optimisation

obsdiscovery: add a test where some common node are hidden This is useful to prevent regression.