cli: Write test for merge commits with patches

radicle-cli/examples/rad-merge-no-ff.md

@@ -0,0 +1,42 @@
+Let's test that merge commits are handled properly in the context of patches.
+First, let's create a patch.
+``` (stderr) RAD_SOCKET=/dev/null
+$ git checkout -b feature/1 -q
+$ git commit --allow-empty -q -m "First change"
+$ git push rad HEAD:refs/patches
+✓ Patch 143bb0c962561b09e86478a53ba346b5ff934335 opened
+To rad://z42hL2jL4XNk6K8oHQaSWfMgCL7ji/z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi
+ * [new reference]   HEAD -> refs/patches
+```
+
+Then let's update the master branch so that merging the patch would create a merge commit.
+```
+$ git checkout master -q
+$ git commit --amend --allow-empty -q -m "Concurrent change"
+$ git rev-parse HEAD
+f65977beef04fcc5cd5395feed7ff4c37cd90a2f
+```
+
+Now let's merge the patch, creating a merge commit. We can see that one of the
+parents is the patch head.
+```
+$ git merge feature/1 -q --no-ff
+$ git show --format=raw HEAD
+commit 737a10cfa29111afeb0d43cf3545cee386b939ec
+tree b4eecafa9be2f2006ce1b709d6857b07069b4608
+parent f65977beef04fcc5cd5395feed7ff4c37cd90a2f
+parent 20aa5dde6210796c3a2f04079b42316a31d02689
+author radicle <radicle@localhost> 1671125284 +0000
+committer radicle <radicle@localhost> 1671125284 +0000
+
+    Merge branch 'feature/1'
+
+```
+
+Finally, we push master and expect the patch to be merged.
+``` (stderr) RAD_SOCKET=/dev/null
+$ git push rad master
+✓ Patch 143bb0c962561b09e86478a53ba346b5ff934335 merged
+To rad://z42hL2jL4XNk6K8oHQaSWfMgCL7ji/z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi
+   f2de534..737a10c  master -> master
+```

radicle-cli/tests/commands.rs

@@ -1099,6 +1099,31 @@ fn rad_merge_after_update() {
     .unwrap();
 }
 
+#[test]
+fn rad_merge_no_ff() {
+    let mut environment = Environment::new();
+    let alice = environment.node(Config::test(Alias::new("alice")));
+    let working = environment.tmp().join("working");
+
+    fixtures::repository(working.join("alice"));
+
+    test(
+        "examples/rad-init.md",
+        working.join("alice"),
+        Some(&alice.home),
+        [],
+    )
+    .unwrap();
+
+    test(
+        "examples/rad-merge-no-ff.md",
+        working.join("alice"),
+        Some(&alice.home),
+        [],
+    )
+    .unwrap();
+}
+
 #[test]
 fn rad_patch_pull_update() {
     logger::init(log::Level::Debug);