Flux unconditionally pushes a sync tag on each loop, whether or not anything has changed

[paddycarey]

I've noticed that when running fluxd in my cluster, that the sync tag in my Git repo is updated and pushed each time flux loops, whether or not any changes have been made to the repository.

I am running Flux 1.8.1 on EKS with K8s 1.10, installed using the helm chart in the weaveworks/flux repo.

Flux is otherwise functioning as expected and this has no impact on the K8s cluster itself or how things are deployed/managed by flux. The only real impact this has (for us) is that it keeps the repo we use for keeping manifests in at the top of the list of recently updated repos in Github, and throws off some of the tools we use for collecting git metrics.

Link to further discussion in Weave Users slack: https://weave-community.slack.com/archives/C4U5ATZ9S/p1542624736954700

Discussion with @squaremo pointed to this line as the culprit: https://github.com/weaveworks/flux/blob/master/daemon/loop.go#L416