cli: Add progress information to scanner scan command
Add a generic callback method for the scan command to retrieve and display progress information. It takes a context argument to distinguish the caller. Adapt the existing policy discovery callback.
The progress information for now is shown for the following steps:
- Directory.from_disk, the local file discovery step
- Policy.discovery, the SWH archive discovery step
Depends on swh-model!344 (merged)
Edited by Franck Bret