evolve: improve error messages when conflicts occur This patch improves the error messages when conflicts occur. First, we drop the line 'evolution failed', that is not the best line we can show and evolution didn't failed, it's just interrupted by the conflicts and when user will run `hg evolve --continue`, things will be fine. I still remember when I first saw 'evolution failed', I got a bit scare as am I in a recoverable position or not. So let's drop this scary line. Second, we replace the error messages to say `resolve conflicts and see help-topic`. The help topic was added recently and documents all the three flags very well. Addition of tests also showed that all the three flags works fine with all the three instability type. So we should advertise them more. Third, we now raise the error with our error message rather than raising MergeFailure and having evolution related text in hint or stderr above. This increase the focus on the error message we want to show. After this patch, I think error messages by evolve in case of conflicts will be same in every case.

evolve: point to `hg help evolve.interrupted` while resolving content-div Recent test additions shows that --abort and --stop works well while resolving content-divergence and we should advertise them. This patch does so by pointing to evolve.interrupted help topic.

tests: add test about aborting content-divergence when multiple parents This patch adds tests for --abort flag of hg evolve command when we are resolving content-divergence which are on different parents and parent of one of them is the gca of both of them. The tests shows that we are doing good and we should advertise the flag during conflicts.