Add 2 options --noattrcache --nodatacache

[benrubson]

Hi,

This PR adds 2 new options :
--noattrcache : disables attr cache only.
--nodatacache : disables data cache only.

So this is in addition to the existing one :
--nocache : disables attr and data cache.

Thank you 👍

Ben

[rfjakob]

Hmm. What is the use case here?

[benrubson]

Current "problem" is that if you want to cache attributes for a small amount of time, with let's say for example -oattr_timeout=0.1, then data is cached without timeout.
With this PR you can then do --nodatacache -oattr_timeout=0.1.
I then also added --noattrcache for consistency.

[rfjakob]

Why would you want that? Shouldn't the user just use --nocache to be safe?

[rfjakob]

If there is a user need for this, we should do it, but if not, I'd suggest to keep things as simple as possible

[benrubson]

On some systems you may like to have a small attributes' cache to speed-up directory listing during which you can get several subsequent getattr operations for the same item.
However, data cache may not be desired.
This is why I implemented the possibility to fine-tune cache.

[rfjakob]

Ok, if you think it is useful, let's go for it

[benrubson]

Thank you @rfjakob 👍