Add a new `pipeline github sync branches` command that can synchronize
two branches. We'll use this to synchronize the
`hashicorp/vault-enterprise/ce/*` branches with `hashicorp/vault/*`.
As the community repository is effectively a mirror of what is hosted in
Enterprise, a scheduled sync cadence is probably fine. Eventually we'll
hook the workflow and sync into the release pipeline to ensure that
`hashicorp/vault` branches are up-to-date when cutting community
releases.
As part of this I also fixed a few static analysis issues that popped up
when running `golangci-lint` and fixed a few smaller bugs.
Signed-off-by: Ryan Cragun <me@ryan.ec>
