[Storage] Dataset Symlink Issue

[michaelzhiluo]

Sky will not upload dataset/sync file mount IF the dataset path is a symlink to the actual dataset path.

[romilbhardwaj]

Symlinks can be quite hairy - we can start by simply putting a warning in the documentation that users should not put symlinks in their workdir/mounts.

[gmittal]

Can we use os.path.islink to throw an exception/warning if a user puts a symlink in the mounts/workdir?

[michaelzhiluo]

The hard part is if the workdir is not symlinked, but a SUBDIRECTORY is symlinked. This is pretty nasty to fix.

[concretevitamin]

aws/aws-cli#453