replication: update delegate on fast-forward

When a delegate's rad/id already exists we check that the
rad/ids/<urn.id> for the project being replicated is a fast-forward for
rad/id. If that's the case we can safely update the rad/id to the latest
tip.

The `fast_forward` function works as follows:
1. Get tip of rad/id
2. Check the verified person's tip is a descendant of 1.
3. If so, update rad/id

Signed-off-by: Fintan Halpenny <[email protected]>

librad/src/git/identities/person.rs

@@ -5,7 +5,7 @@
 
 use std::{convert::TryFrom, fmt::Debug};
 
-use radicle_git_ext::{is_not_found_err, OneLevel};
+use radicle_git_ext::{self as ext, is_not_found_err, OneLevel};
 
 use super::{
     super::{
@@ -189,6 +189,21 @@ where
     Ok(verified(storage).newer(a, b)?)
 }
 
+pub fn fast_forward(storage: &Storage, latest: &VerifiedPerson) -> Result<Option<ext::Oid>, Error> {
+    let urn = latest.urn().with_path(None);
+    let id_ref = super::common::IdRef::from(&urn);
+    let canonical = id_ref.oid(storage)?;
+    let tip = latest.content_id;
+    Ok(if storage.as_raw().graph_descendant_of(*tip, *canonical)? {
+        id_ref
+            .update(storage, tip, &format!("fast-forward to {}", tip))
+            .map_err(|e| Error::Store(e.into()))?;
+        Some(tip)
+    } else {
+        None
+    })
+}
+
 fn identities<S>(storage: &S) -> Identities<Person>
 where
     S: AsRef<storage::ReadOnly>,

librad/src/git/replication.rs

@@ -805,9 +805,15 @@ mod project {
         project_urn: &Urn,
     ) -> Result<(), Error> {
         let delegate_urn = person.urn();
-        ensure_rad_id(storage, &delegate_urn, person.content_id)?;
-        tracking::track(storage, &delegate_urn, peer)?;
-        tracking::track(storage, project_urn, peer)?;
+
+        // if the identity is known we see if we can fast-forward it
+        if storage.has_urn(&delegate_urn)? {
+            identities::person::fast_forward(storage, person)?;
+        } else {
+            ensure_rad_id(storage, &delegate_urn, person.content_id)?;
+            tracking::track(storage, &delegate_urn, peer)?;
+            tracking::track(storage, project_urn, peer)?;
+        }
 
         // Now point our view to the top-level
         symref(
@@ -927,7 +933,7 @@ mod project {
         S: AsRef<storage::ReadOnly>,
     {
         let storage = storage.as_ref();
-        identities::project::verify_with(storage, &urn, |delegate| {
+        identities::project::verify_with(storage, urn, |delegate| {
             let refname =
                 Reference::rad_delegate(Namespace::from(urn.clone()), &delegate).with_remote(peer);
             storage.reference_oid(&refname).map(|oid| oid.into())

test/src/test/integration/librad/scenario/updated_delegate.rs

@@ -1,4 +1,4 @@
-// Copyright © 2019-2020 The Radicle Foundation <[email protected]>
+// Copyright © 2021 The Radicle Link Contributors
 //
 // This file is part of radicle-link, distributed under the GPLv3 with Radicle
 // Linking Exception. For full terms see the included LICENSE file.