- Change rclone/fs interfaces to accept context.Context
- Update interface implementations to use context.Context
- Change top level usage to propagate context to lover level functions
Context propagation is needed for stopping transfers and passing other
request-scoped values.
This puts a shim on the reader opened by Copy so that if an error is
returned, the reader is re-opened at the correct seek point.
This should make downloading very large files more reliable.