rebase: move actual rebase into a single transaction...
rebase: move actual rebase into a single transaction
Previously, rebasing would open several transaction over the course of rebasing
several commits. Opening a transaction can have notable overhead (like copying
the dirstate) which can add up when rebasing many commits.
This patch adds a single large transaction around the actual commit rebase
operation, with a catch for intervention which serializes the current state if
we need to drop back to the terminal for user intervention. Amazingly, almost
all the tests seem to pass.
On large repos with large working copies, this can speed up rebasing 7 commits
by 25%. I'd expect the percentage to be a bit larger for rebasing even more
commits.
There are minor test changes because we're rolling back the entire transaction
during unexpected exceptions instead of just stopping mid-rebase, so there's no
more backup bundle. It also leave an unknown file in the working copy, since our
clean up 'hg update' doesn't delete unknown files.
