If anonymize=True in "write..." and Brainvision --> DO NOT convert to BrainVision

[sappelhoff]

Currently, all EEG files are converted to BrainVision format if anonymize is set in write_raw_bids.

for data that is already in BrainVision format, this means that it's unnecessarily re-written using pybv.

A cleaner (IMO more sensible and less error prone) alternative would be to write a short snippet of code in MNE-BIDS that ...

• copies the BrainVision files to BIDS and then ...
• goes through the .vmrk file
• identifies the lines in .vmrk that contain the recording date
• replace this recording date with the anonymized date

[agramfort]

this makes then BV a special case. For me it's more to be used as a unit-test.

my 2c

[sappelhoff]

together with #469 we'd have "two special cases" --> I just say that if we can achieve anonymization with a few lines of code WITHOUT having to change the original data format ... then that's better than data format conversion.

[agramfort]

fair enough