Revert "Add GitRepo#owner, for easier stubbing."

This reverts commit 074292e0c451db7676346cd647198b43c382adc4.
Set git details using the root path's owner.

At this point the repo doesn't exist so we can't query its root's owner.
Clean up dep snapshot specs: assume the repo exists.

The create/init/commit/run/commit logic is tested in the GitFS specs. The point of the dep snapshotting specs is to ensure snapshots are taken only when deps are successfully met, and only when snapshotting is enabled.
Merge branch 'git-fs-initing'