rebase: teach in-memory rebase to not restart with on-disk rebase on conflict...
rebase: teach in-memory rebase to not restart with on-disk rebase on conflict
When in-memory rebase runs into conflicts, it redoes the whole rebase
operation. This patch teaches it to instead discard just the current
`overlayworkingctx` and redo that node on disk.
I've tested this by enabling in-memory rebase by default and checking
that there are no unexpected differences after this patch.
The next step is to make it so that `hg rebase --continue` can use
in-memory merge.
Differential Revision:
https://phab.mercurial-scm.org/D9076
