evolve: move logic to complete interrupted relocation to new fn
This moves logic which completed the interrupted relocation to it's own separate
function as we will need that function in continuing phase-divergence and
content-divergence too.
#require test-repo pyflakes
Copied from Mercurial core (60ee2593a270)
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:(**.py or grep("^#!.*python")) - removed()' 2>/dev/null \
> | xargs pyflakes 2>/dev/null