Remove Seemingly Redundant "git fetch" Operations

[jordan-wright]

Auto-reviewers: @NiharikaRay @matthewwardrop @earthmancash @danfrankj

I could be wrong (in which case, please don't hesitate to close this out), but it seems that some knowledge repo updates may be unnecessary. For example, running knowledge_repo create, knowledge_repo preview, and others may not require a full update to complete successfully.

It's not a huge deal, but if we have git hooked up to an HSM like a yubikey, I have to approve the fetch every time, which can get repetitive.

If this is something y'all would be interested in, let me know and I'll be happy to take it on.