core/stats can return two different schemas in 'transferring' field.
One is object with fields the other is just plain string.
This is confusing, unnecessary and makes defining response schema
more difficult. It also returns `lastError` as value which can be
rendered differently depending on source of error.
This change standardizes 'transferring' filed to always return
object but with reduced fields if they are not available.
Former string item is converted to {name:remote_name} object.
'lastError' is forced to be a string as in some cases it can be encoded
as an object.
Introduce stats groups that will isolate accounting for logically
different transferring operations. That way multiple accounting
operations can be done in parallel without interfering with each other
stats.
Using groups is optional. There is dedicated global stats that will be
used by default if no group is specified. This is operating mode for CLI
usage which is just fire and forget operation.
For running rclone as rc http server each request will create it's own
group. Also there is an option to specify your own group.
This is done to make clear ownership over accounting object and prepare
for removing global stats object.
Stats elapsed time calculation has been altered to account for actual
transfer time instead of stats creation time.
- 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.
