This PR adds guards to prevent creating filesets with multiple files that have the same path.
While it should technically be impossible to have multiple entries that have the same path, it could happend either due to glitches or because the source data (manual lists, remote sources, etc) returns duplicates.
This PR adds a simple check for each folder to ensure that on a folder-level, duplicate paths cannot be introduced.
There is also a post-backup check to evict any duplicates, and the recreate process will reject duplicate paths.
Finally, the repair command will remove duplicates if they somehow manage to get into the database anyway.
A database-level prevention is not currently feasible as it needs a cross-table check for uniqueness, which requires more work from the database to check for each added file. Since this is expected to be a very rare event, the added processing was not justified.
Kenneth Skovhede
e7aa60fba0