amend: allow aborting an `amend --patch` by saving an empty file (issue5925) This patch fixes issue5925 by allow aborting a `hg amend --patch` call by saving an empty patch file. This is similar to aborting of `hg amend` when commit message is empty. Test changes demonstrate the fix.

tests: add a test to demonstrate issue5925 The issue will be fixed in next patch.

test: fix possible output change from 4.7 Change in debug timing can display these extra messages.

state: add the get() method that evolvecmd:1836 expects

rewing: prevent rewind in case of uncommitted changes rewind can update, which means merge and troubles. We might relax this limitation in the future.

rewind: default to rewinding the current stack

rewing: add the ability to rewind "from" revisions

evolve: exclude "identical" precursors from the precursors set I'm not sure it is the right thing to do, but it simply thing a lot for now. Otherwise, using 'precursors' to find rewind direction become too complex. This is going to give problematic result in case of prune. Since there are no other precursors to follow.

rewind: move revision selection into its own function This will help making the logic more advanced.

rewind: automatically rewind entire stack We now rewind the full stack, avoiding creating orphans. A `--exact` flag is added to force rewinding only the explicitly specified changesets.