merge: make low-level update() private (API)
We have very few callers left that call the low-level `merge.update()`
function. I think it's time to make it private. I'll remove the
remaining callers in coming patches, except for one call from the
`rebase` module. I hope to eventually fix that too, but it's more
complex because it requires teaching `merge.graft()` to work with a
dirty working copy.
Differential Revision: https://phab.mercurial-scm.org/D9065
== New Features ==
* `hg mv -A` can now be used with `--at-rev`. It behaves just like
`hg cp -A --at-rev`, i.e. it marks the destination as a copy of the
source whether or not the source still exists (but the source must
exist in the parent revision).
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
* `merge.update()` is now private (renamed to `_update()`). Hopefully
the higher-level functions available in the same module cover your
use cases.