scmutil: handle conflicting files and dirs in origbackuppath
When ui.origbackuppath is set, .orig files are stored outside of the working
copy. However conflicts can occur when files or directories end up having the
same name. These conflicts cause Mercurial to abort, even if they've been
created as a result of different backups.
Make sure we always replace files or directories in the origbackuppath if
they conflict with another file or directory.
Test Plan:
Add new unit test for conflicting paths.
Differential Revision: https://phab.mercurial-scm.org/D680
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.