Merge branch 'ps/hash-and-ref-format-from-config'

The default object hash and ref backend format used to be settable only with explicit command line option to "git init" and environment variables, but now they can be configured in the user's global and system wide configuration. * ps/hash-and-ref-format-from-config: setup: make ref storage format configurable via config setup: make object format configurable via config setup: merge configuration of repository formats t0001: delete repositories when object format tests finish t0001: exercise initialization with ref formats more thoroughly