Add option to verify checksum without requiring write access to remote objects

[ghuls]

Add option to verify checksum without requiring write access to remote objects and without requiring to upload new data.

I wanted to check some data uploaded by another user, which I can read, but with the current mango-ingest, I can't verify the checksums as it requires write permissions to remote object by default.

Trying to run the --dry-run option with --verify-checksum does not work for just checking the checksum as it will just print dry-run: would upload /path/to/file

$ mango_ingest.py -r -p local_dir/ -d /irods --verify-checksum --verbose --no-watch --dry-run

[paulborgermans]

Indeed, checksum operations require write access to the object by the user executing the code. That is not something that I/we can change as it is the way the irods backend works. Maybe a stricter checking of access rights should be added?

[ghuls]

I don't see why it shouldn't be possible to retrieve a precalculated checksum from iRODS as a user with read only rights. If that is really not possible it is something that should be fixed in the iRODS backend.