There is something weird going on with the way VE sets the If-Match header when sending requests to RESTBase. We are facing two problems:
- VE sends an ETag that is suffixed with -df (was T230272)
- VE doesn't send the If-Match header at all (was T206029)
In both cases, it is not clear when/how/why the ETag is modified/removed. We should investigate this further and find the root cause for this. Currently, we have two work-arounds in RESTBase allowing normal operation despite these problems, but they are ugly hacks and should be removed as soon as possible.