Config:
```
- type: push
...
conflict_resolution:
initial_replication: most_recent | all | fali
```
The ``initial_replication`` option determines which snapshots zrepl
replicates if the filesystem has not been replicated before.
If ``most_recent`` (the default), the initial replication will only
transfer the most recent snapshot, while ignoring previous snapshots.
If all snapshots should be replicated, specify ``all``.
Use ``fail`` to make replication of the filesystem fail in case
there is no corresponding fileystem on the receiver.
Code-Level Changes, apart from the obvious:
- Rework IncrementalPath()'s return signature.
Now returns an error for initial replications as well.
- Rename & rework it's consumer, resolveConflict().
Co-authored-by: Graham Christensen <graham@grahamc.com>
Fixes https://github.com/zrepl/zrepl/issues/550
Fixes https://github.com/zrepl/zrepl/issues/187
Closes https://github.com/zrepl/zrepl/pull/592
