evolve: fixed lock acquire before checking state
Before checking the states `repo.lock()` and `repo.wlock()` need
to be acquired. This was not happening in `evolve()` earlier.
This patch creates a seperate `_performevolve()` funtion which
can be then called with locks acquired.
This also removes the redundant lock acuquiring of `abortevolve`
and `continueevolve` as lock is now taken earlier.
Martin von Zweigbergk <martinvonz@google.com> [Wed, 31 Jul 2019 10:52:14 -0700] rev 4796
py3: add back a progress(0) call lost in 8664231b47ac
I don't think it really matters, but it wasn't intentional, so let's
just restore the old behavior.