Is there a reason for abi-xx feature flags?

[stepancheg]

libfuse does not seem to use such flags, and just enable max version unconditionally. https://github.com/libfuse/libfuse/blob/master/include/fuse_kernel.h#L277

Protocol seems to negotiate properly even if max supported version is specified.

I could guess that can be done to not enable newest not well tested features, but if this is not the case, this is probably better done with runtime flag?

[cberner]

Oh interesting. The real reason the flags are there is legacy. The flags were there before I forked fuser off of fuse-rs, and I've just kept them around.

It'd be great if we can remove them. We should check that MacFUSE can handle the max version. IIRC, it only supports up to ABI 7.19, and it's implementation is non-standard in various ways. I don't really like supporting it, but enough people use it that I've kept support