Feature request: git_resource should optionally "git pull" when update requested

[CpuID]

Would be nice for git_resource to do a git pull if an update is requested for a resource (hitting the refresh in the UI). So we can pull in changes to upstream dependencies, and include them as part of a fresh build.

Should be optional, via a feature flag.

[CpuID]

Interesting, it looks like it does a git fetch -a origin && git checkout -f origin/master && git submodule update --init when you hit refresh on the Tiltfile itself, but not on the resource (eg. some K8s service)?