On push, we check whether the resulting state would cause a
divergence/fork in the canonical head, and if so, prevent the push from
happening.
This is to avoid situations where delegates have to then rollback their
heads.
Note that this doesn't prevent forks from happening altogether, as they
could happen asychronously, but it mitigates the problem.
This is a fairly substantial change, which adds a new configuration file
to the user's `$RAD_HOME` that includes node configuration, including
the alias, and also makes node aliases required.
When running `rad auth`, the user is now prompted for an alias, which
defaults to `$USER`.
When running `rad self`, the alias is now shown.
If the user runs radicle without a config file, the defaults are loaded,
and `$USER` is used as the alias.
This adds the ability to the git-remote-helper to open and update
patches via a `git push` to the magic ref `refs/patches` and
`refs/heads/patches/<patch-id>`.
The main change is that we had to move away from offering the `connect`
capability in the remote helper, to offering `push` and `fetch`
individually.
To get a feel for how this works, see the `rad-patch-via-push.md`
example.
Alexis Sellier
cloudhead