Render whole-file patches from change metadata

server/src/session/driver.rs

@@ -470,6 +470,18 @@ pub(super) fn patch_start(id: String, diff: String) -> Event {
     }
 }
 
+pub(super) fn prefixed_lines(prefix: char, text: &str) -> String {
+    text.split_inclusive('\n')
+        .map(|line| {
+            if line.ends_with('\n') {
+                format!("{prefix}{line}")
+            } else {
+                format!("{prefix}{line}\n")
+            }
+        })
+        .collect()
+}
+
 /// How much the model was holding, from the three figures a turn reports:
 /// the input side only, prompt plus both cache figures. A cached token is
 /// cheaper but it is still one the model was given; output is what the turn