subrepo: use safehasattr instead of hasattr
Some of these instances could be rewritten as clever getattr(x, y,
default) ladders, but that felt like it impeded readability too much
to be worth the modest efficiency gain.
Test update logic when there are renames
Update with local changes across a file rename
$ hg init
$ echo a > a
$ hg add a
$ hg ci -m a
$ hg mv a b
$ hg ci -m rename
$ echo b > b
$ hg ci -m change
$ hg up -q 0
$ echo c > a
$ hg up
merging a and b to b
warning: conflicts during merge.
merging b failed!
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
$ cd ..