diff: replace --merge option by config option
I can't think of any reason you'd want to enable the merge diff on a
run-to-run basis; you'd probably either always or never want it set
(though I can't see why you'd never want it set). If you have it set,
you'll probably also want the same output in `hg log -p`
output. Having a single config option for the feature makes sense.
Differential Revision: https://phab.mercurial-scm.org/D9956
== New Features ==
* `hg purge` is now a core command using `--confirm` by default.
* The `rev-branch-cache` is now updated incrementally whenever changesets
are added.
== New Experimental Features ==
* There's a new `diff.merge` config option to show the changes
relative to an automerge for merge changesets. This makes it
easier to detect and review manual changes performed in merge
changesets. It is only supported by `hg diff --change` so far.
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
* `changelog.branchinfo` is deprecated and will be removed after 5.8.
It is superseded by `changelogrevision.branchinfo`.