surf: add simple copy detection to diff

Signed-off-by: Sebastian Martinez <me@sebastinez.dev>

radicle-surf/src/repo.rs

@@ -519,6 +519,7 @@ impl Repository {
         // Detect renames by default.
         let mut find_opts = git2::DiffFindOptions::new();
         find_opts.renames(true);
+        find_opts.copies(true);
         diff.find_similar(Some(&mut find_opts))?;
 
         Ok(diff)

radicle-surf/t/src/diff.rs

@@ -302,7 +302,13 @@ fn test_diff_serde() -> Result<(), Error> {
             "oldPath": "text/emoji.txt",
             "newPath": "emoji.txt",
         }],
-        "copied": [],
+        "copied": [{
+            "diff": {
+                "type": "empty",
+            },
+            "newPath": "file_operations/copied.md",
+            "oldPath": "README.md",
+        }],
         "modified": [{
             "path": "README.md",
             "diff": {
@@ -343,7 +349,7 @@ fn test_diff_serde() -> Result<(), Error> {
         }],
         "stats": {
             "deletions": 9,
-            "filesChanged": 4,
+            "filesChanged": 5,
             "insertions": 4,
         }
     });