evolve: extract function for relocating divergent commit There was some duplication here, so let's extract to a function. I'm going to add a little bit more shared code next.

caches: preserve permissions of top-level .hg When using hg on a shared filesystem on UNIX, cache files normally inherit the permissions of the .hg directory. This is most commonly used to ensure everything is writable by all users. The sqlite3 cache files don't have a way to directly set the permission, so check if a special mode is necessary and try to apply them to newly created database files.