obsfate: fix changeset description diff computing Mercurial core 8b6dd3922f70 changed the mdiff.unidiff API. Add a new compat method for all supported Mercurial versions.

evolve: add comptability to read old evolvestate files When a user runs `hg evolve` with old evolve where we used to write evolvestate the old ways i.e. without using cbor, and faces conflicts, the evolve is interrupted. If the user updates evolve before completing the evolve, that can result in traceback as the new evolve cannot read the old evolvestate file. The previous patch added function to read old evolvestate file and this patch uses that when we encounter the above mentioned case.

state: bring back the function to read old evolvestate files Before introduction of this nice cmdstate file wrapper, we had individual methods to write data to evolvestate file. Let's bring back the function which used to read data from the old evolvestae file so that we can use it in next patch for BC purposes.

evolve: add entry in CHANGELOG about fixed behavior of `hg evolve --continue`

evolve: store the skippedrevs in evolvestate While doing `hg evolve`, there are some revs which are skipped as they can't be evolved. Before this patch, we did not store this information in evolvestate and neither they were evolved, so `hg evolve --continue` will again try to stabilize those revisions. As much time as we run `hg evolve --continue`, this will happen which is not a good behavior. This patch adds a skippedrevs list to evolvestate where we store such revisions so that we don't try to stabilize them again.

evolve: show the updated working directory after `hg evolve --continue` `hg evolve` shows a nice message about the new working directory when the evolve ends but if the evolve is interrupted by conflicts and you continue the evolve resolving the conflicts, that nice message is lost. Let's have that in case of `--continue` too.

evolve: make `hg evolve --continue` respect `--confirm` Previous patch added capability to `hg evolve --continue` to continue the rest of the stack, not just the current revision but that was missing respecting the `--confirm` flag which user passed earlier. This patch makes sure we respect the `--confirm` flag.

evolve: make `--continue` continue evolving all remaining revisions This patch makes `hg evolve --continue` to continue all remaining revisions instead of just the current conflicted one. There are some still improvements required to this behavior after which the CHANGELOG entry will be added.

tests: add more tests to test-evolve-continue.t This patch adds more tests for `hg evolve --continue`. The tests demonstrates how the continuation handling of hg evolve is broken and the later patches fixes that handling.

evolve: handle case when newnode can be None while continuing evolve There can be case when `hg evolve --continue` is run, when working directory is clean and there is nothing to be included in the new commit. Let's make sure we handle such cases correctly and obsolete the node which is evolved with parent of wdir as successor. This is same as what rebase does.