evolve: use context manager for transactions

evolve: use consistent message and just re-raise InterventionRequired

evolve: use standard InterventionRequired instead of MergeFailure

evolve: don't use exception for local flow control The LocalMergeFailure class was added in 3f91654713dd (obsolete Move merge failure handling into stabilize code, 2012-08-20). I think the "if compat.hasconflict(r)" check was added later. Now that we have that check, we should use that for flow control instead. Note that this means that any unexpected exception from _relocatecommit() will now just raise (and roll back the transaction). I think that's an improvement.

evolve: reduce indentation with an early return statement

evolve: remove a useless return statement at end of function

test: move a test to an appropriate test file This patch introduce a new test file test-evolve-orphan-corner-cases.t for tests which covers corner cases.

test: improve the title of a test

test: remove duplicated test We have the test in test-evolve-orphan-split.t which is covering the same case this test does. Also this test states that evolve shows some error in split case, but now this is not the case we update to the top of splitted csets.

evolve: warn user for the metadata being lost in public divergence resolution This patch print warnings if some "extras" of a divergent changeset that is possibly important metadata which is being lost during the resolution of public divergence.