copy-tracking: minor rearrangement of match arms for didactic reasons

This could be squashed into parent, but the parent commit's diff seems
easier to review without this change.

Author: ilyagr

lib/src/copies.rs

@@ -411,6 +411,15 @@ async fn classify_diff_entry(
             Some(TreeValue::File { copy_id: id2, .. }),
         ) if id1 == id2 => vec![CopyHistoryTreeDiffEntry::normal(diff_entry)],
 
+        // New file with copy history — needs copy-tracing.
+        (None, Some(f @ TreeValue::File { .. })) => {
+            let f = f.clone();
+            vec![CopyHistoryTreeDiffEntry {
+                target_path: diff_entry.path,
+                diffs: diffs_from_copies(before_tree, after_tree, f).await,
+            }]
+        }
+
         // For files with non-matching copy-ids, or for a non-file that changes to a
         // file, mark the first as deleted and do copy-tracing on the second.
         //
@@ -445,15 +454,6 @@ async fn classify_diff_entry(
             ]
         }
 
-        // New file with copy history — needs copy-tracing.
-        (None, Some(f @ TreeValue::File { .. })) => {
-            let f = f.clone();
-            vec![CopyHistoryTreeDiffEntry {
-                target_path: diff_entry.path,
-                diffs: diffs_from_copies(before_tree, after_tree, f).await,
-            }]
-        }
-
         // Anything else (e.g. file => non-file non-tree), issue a simple diff entry.
         //
         // NOTE[deletion-diff-entry2]: this is another point where a spurious deletion entry