vfsproxy: inherit the `createmode` attribute too It is an important part of the API when creating directory. We will need it in the next changeset.

revlog: test more complex file pattern for revlog split There have been a report of failure while splitting revlog. The file name involved was important. The pattern involved here are not problematic, but it help to setup the machinery to test multiple files, the actual fix and problematic file will arrive in a later changeset.