Explore ways to share workdir across resources

[soichih]

Bigred2 / Karst / Carbonate all shares the same file system. There is no point of copying / duplicating workdirs across these resources.

I've been trying to find a way to make inter-resource rsyncing of task directories that happens to be the identical file system to work with no side effects. The most recent attempt to set -K(keep-dirlinks) option on rsync would fail for symlinks inside another directory probably because the directory gets renamed(?) while being processed. --inplace should workaround this, but it didn't.

Instead of relying on rsync, I think I should add some kind of check to see if src/dest workdir is actually the same file system by comparing the inode #, or do something along that line and don't even bother running rsync.

If this works, then user can configure the same workdir for all 3 clusters (BR2/Karst/Cargonate) to reduce disk usage and unnecessary syncing of input data.