cli: test missing commits for canonical quorum

Test the scenario where 2 delegates are collaborating, where one delegate is
missing the other's commit while pushing to the default branch.

crates/radicle-cli/examples/rad-id-missing-commits.md

@@ -0,0 +1,90 @@
+Sometimes, commits may appear missing in the working copy when pushing to the
+default branch. In this scenario, we show this happening, and then how to
+recover from the problem.
+
+First, we need to be in a scenario where there is more than one delegate:
+
+``` ~alice
+$ rad id update --title "Add Bob" --description "Add Bob as a delegate" --delegate did:key:z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk -q
+7be665f9fccba97abb21b2fa85a6fd3181c72858
+```
+
+``` ~alice
+$ rad follow did:key:z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk
+✓ Follow policy updated for z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk
+$ rad sync
+Fetching rad:z42hL2jL4XNk6K8oHQaSWfMgCL7ji from the network, found 1 potential seed(s).
+✓ Target met: 1 seed(s)
+🌱 Fetched from z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk
+✓ Synced with 1 seed(s)
+$ rad id update --title "Bump threshold" --description "Bumping threshold to 2" --threshold 2 -q
+f515dc5af139b8eb9fa817df3f637f2acc29c12b
+$ rad sync -a
+✓ Synced with 1 seed(s)
+```
+
+``` ~bob
+$ rad id accept f515dc5af139b8eb9fa817df3f637f2acc29c12b -q
+$ rad sync -a
+✓ Synced with 1 seed(s)
+```
+
+At this stage, Bob makes some changes at the same time, updating the default
+branch:
+
+``` ~bob (stderr) RAD_SOCKET=/dev/null
+$ touch README.md
+$ git add README.md
+$ git commit -m "Add README"
+$ git push rad master
+To rad://z42hL2jL4XNk6K8oHQaSWfMgCL7ji/z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk
+   f2de534..361f146  master -> master
+```
+
+Alice, is also busy making some changes:
+
+``` ~alice
+$ rad sync -f
+Fetching rad:z42hL2jL4XNk6K8oHQaSWfMgCL7ji from the network, found 1 potential seed(s).
+✓ Target met: 1 seed(s)
+🌱 Fetched from z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk
+```
+
+``` ~alice
+$ touch LICENSE
+$ git add LICENSE
+$ git commit -m "Add LICENSE"
+[master 62d19fd] Add LICENSE
+ 1 file changed, 0 insertions(+), 0 deletions(-)
+ create mode 100644 LICENSE
+```
+
+However, when she goes to push to the default branch she sees an error about a missing commit from Bob:
+
+``` ~alice (fails) (stderr)
+$ git push rad master
+error: the commit 361f146ec7339fffdea1ea586f51410250bec9cf for did:key:z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk is missing from the repository [..]
+error: failed to push some refs to 'rad://z42hL2jL4XNk6K8oHQaSWfMgCL7ji/z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi'
+```
+
+The reason for this is that when attempting to compute the canonical commit for
+the default branch, there are some checks to see if the delegates agree on the
+new commit. In this case, Bob's commit was not available to perform this check,
+so, Alice must fetch from Bob's state of the repository. She can do this by
+adding him as a remote:
+
+``` ~alice
+$ rad remote add did:key:z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk --name "bob"
+✓ Remote bob added
+✓ Remote-tracking branch bob/master created for z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk
+```
+
+
+``` ~alice (stderr) RAD_SOCKET=/dev/null
+$ git push rad master
+To rad://z42hL2jL4XNk6K8oHQaSWfMgCL7ji/z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi
+   f2de534..62d19fd  master -> master
+```
+
+Note that if the remote tracking branch already exists, then she can simply `git
+fetch bob/master`.

crates/radicle-cli/tests/commands.rs

@@ -443,6 +443,47 @@ fn rad_id_threshold_soft_fork() {
     .unwrap();
 }
 
+#[test]
+fn rad_id_missing_commits() {
+    let mut environment = Environment::new();
+    let alice = environment.node("alice");
+    let bob = environment.node("bob");
+    let acme = RepoId::from_str("z42hL2jL4XNk6K8oHQaSWfMgCL7ji").unwrap();
+
+    environment.repository(&alice);
+
+    test(
+        "examples/rad-init.md",
+        environment.work(&alice),
+        Some(&alice.home),
+        [],
+    )
+    .unwrap();
+
+    let mut alice = alice.spawn();
+    let mut bob = bob.spawn();
+
+    bob.handle.seed(acme, Scope::All).unwrap();
+    alice.connect(&bob).converge([&bob]);
+
+    bob.fork(acme, environment.work(&bob)).unwrap();
+
+    formula(&environment.tempdir(), "examples/rad-id-missing-commits.md")
+        .unwrap()
+        .home(
+            "alice",
+            environment.work(&alice),
+            [("RAD_HOME", alice.home.path().display())],
+        )
+        .home(
+            "bob",
+            environment.work(&bob).join("heartwood"),
+            [("RAD_HOME", bob.home.path().display())],
+        )
+        .run()
+        .unwrap();
+}
+
 #[test]
 fn rad_id_update_delete_field() {
     Environment::alice(["rad-init", "rad-id-update-delete-field"]);