[ci skip] Make the upward merge for non-stable packaging more obvious

The notice to merge upward is easy to miss when pushing the other
branches and the RC tag. Call attention to it with code blocks, and move
the note on resolving merge conflicts from an upward merge into a note.

Perhaps the upward merge merits its own step and thus a renumbering?

Author: NattyNarwhal

docs/release-process.md

@@ -306,10 +306,33 @@ slightly different steps. We'll call attention where the steps differ.
     >
     > Local-only release branches should not be pushed!
 
-    Do not forget to merge up PHP-X.Y all the way to master. When resolving
-    the conflicts, ignore the changes from PHP-X.Y in higher branches. It
-    means using something like `git checkout --ours .` when on PHP.X.Y+1 or
-    master after the merge resulting in the conflicts.
+    Do not forget to merge up PHP-X.Y all the way to master, including any
+    intermediate version branches.
+
+    ```shell
+    # No intermediate version, merge directly to master
+    git checkout master
+    git merge PHP-X.Y
+    ```
+
+    ```shell
+    # One intermediate version, merge upward into master
+    git checkout PHP-X.Y+1
+    git merge PHP-X.Y
+    git checkout master
+    git merge PHP-X.Y+1
+    ```
+
+   > 🗒 **Note** \
+   >  When resolving the conflicts, ignore the changes from PHP-X.Y in higher
+   >  branches. It means using something like `git checkout --ours .` when on
+   >  PHP.X.Y+1 or master after the merge resulting in the conflicts.
+
+   >  ```shell
+   >  git checkout --ours .
+   >  git add -p
+   >  git commit
+   >  ```
 
 11. Run the following using the release tag to export the tree, create the
     `configure` script, and build and compress three tarballs (`.tar.gz`,