Merge #77's side-by-side number fix into the file tree branch

The new test counts rows from the one after the file's header, which sits
a row lower here under the tree's row.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: krishhgg

src/tui/pull_requests/code.rs

@@ -1944,12 +1944,21 @@ fn body(
         _ => "",
     };
     let mut wanted = Vec::new();
+    // The largest number before the change of those lines, which only the left side shows.
+    let mut old_last = 0;
     for (stretch, showing) in stretches.iter().zip(&showings) {
         let end = stretch.first + showing.head + showing.tail + rest(showing.rest);
+        let before = wanted.len();
         wanted.extend(stretch.first..stretch.first + showing.head);
         wanted.extend(end - showing.tail..end);
+        if let Some(&number) = wanted[before..].last() {
+            old_last = old_last.max(stretch.old + (number - stretch.first));
+        }
     }
     let mut found = lines_at(contents, &wanted).into_iter();
+    // Side by side, each side has its own numbers and marks, as the narrower left one has room
+    // for them.
+    let halves = split.then(|| Halves::of(width)).flatten();
     let last = file
         .hunks
         .iter()
@@ -1958,12 +1967,10 @@ fn body(
             old.max(hunk.new_start + hunk.new_count.saturating_sub(1))
         })
         .chain(wanted.last().copied())
+        .chain(halves.map(|_| old_last))
         .max()
         .unwrap_or_default();
     let digits = last.max(1).ilog10() as usize + 1;
-    // Side by side, each side has its own numbers and marks, as the narrower left one has room
-    // for them.
-    let halves = split.then(|| Halves::of(width)).flatten();
     let mut slides = Slides {
         halves,
         ..Slides::default()

src/tui/pull_requests/code/tests.rs

@@ -3752,6 +3752,51 @@ fn unchanged_lines_side_by_side_show_their_number_on_each_side() {
     assert_eq!(slid.widest, "13   l14".width() + BETWEEN.width() + 19);
 }
 
+#[test]
+fn the_numbers_side_by_side_fit_an_unchanged_line_s_old_place() {
+    // Five lines removed at the top put each line after them five places further on the left,
+    // so the last of those shown is old line 10 beside new line 5.
+    let patch = "diff --git a/g.rs b/g.rs
+--- a/g.rs
++++ b/g.rs
+@@ -1,6 +1 @@
+-o1
+-o2
+-o3
+-o4
+-o5
+ l1
+";
+    let mut code = read(slice(patch, None), 0);
+    code.act(Control::File(0), &[]);
+    code.act(Control::Layout, &[]);
+    for place in 0..2 {
+        code.act(Control::Stretch(0, place), &[]);
+    }
+    assert!(code.ask_text(2).is_some());
+    assert!(code.take_text(2, text(numbered(5))));
+    for place in 0..2 {
+        code.act(Control::Stretch(0, place), &[]);
+    }
+    let removed = (1..=5).map(|old| format!("{old:>2} - {:<14}│", format!("o{old}")));
+    let kept = (1..=5).map(|new| {
+        let old = new + 5;
+        format!("{old:>2}   {:<14}│ {new:>2}   l{new}", format!("l{new}"))
+    });
+    assert_eq!(
+        rows(&code, 40)[8..],
+        removed.chain(kept).collect::<Vec<_>>()
+    );
+    // Stacked, an unchanged line shows only its number after the change.
+    code.act(Control::Layout, &[]);
+    let removed = (1..=5).map(|old| format!("{old} - o{old}"));
+    let kept = (1..=5).map(|new| format!("{new}   l{new}"));
+    assert_eq!(
+        rows(&code, 40)[8..],
+        removed.chain(kept).collect::<Vec<_>>()
+    );
+}
+
 #[test]
 fn only_a_file_added_or_deleted_keeps_one_column_side_by_side() {
     let mut code = read(slice(PATCH, None), 0);