feat: add expandable diff excerpts with configurable context

src/editor.rs

@@ -1064,6 +1064,7 @@ pub struct Editor {
     file_explorer_view: FileView,
     count: Option<usize>,
     diff: Option<DiffState>,
+    diff_context_options: (usize, usize),
     next_diff_request: u64,
     outstanding_diff_request: Option<u64>,
 }
@@ -1134,6 +1135,7 @@ impl Editor {
             file_explorer_view: FileView::Tree,
             count: None,
             diff: None,
+            diff_context_options: (10, 15),
             next_diff_request: 0,
             outstanding_diff_request: None,
         };
@@ -1240,6 +1242,13 @@ impl Editor {
         self.diff.as_ref()
     }
 
+    pub(crate) fn set_diff_context_options(&mut self, context_lines: usize, expand_lines: usize) {
+        self.diff_context_options = (context_lines, expand_lines);
+        if let Some(diff) = &mut self.diff {
+            diff.set_context_options(context_lines, expand_lines);
+        }
+    }
+
     pub(crate) fn take_diff_request(&mut self) -> Option<(u64, Operation)> {
         let operation = self.diff.as_mut()?.take_request()?;
         self.next_diff_request = self
@@ -1275,7 +1284,9 @@ impl Editor {
             self.active.mode = Mode::Normal;
         }
         self.outstanding_diff_request = None;
-        self.diff = Some(DiffState::new());
+        let mut diff = DiffState::new();
+        diff.set_context_options(self.diff_context_options.0, self.diff_context_options.1);
+        self.diff = Some(diff);
     }
 
     fn handle_diff(&mut self, input: Input) {