Allow to toggle git hunk diffs (#11080)

Part of https://github.com/zed-industries/zed/issues/4523

Added two new actions with the default keybindings

```
"cmd-'": "editor::ToggleHunkDiff",
"cmd-\"": "editor::ExpandAllHunkDiffs",
```

that allow to browse git hunk diffs in Zed:


https://github.com/zed-industries/zed/assets/2690773/9a8a7d10-ed06-4960-b4ee-fe28fc5c4768


The hunks are dynamic and alter on user folds and modifications, or
toggle hidden, if the modifications were not adjacent to the expanded
hunk.


Release Notes:

- Added `editor::ToggleHunkDiff` (`cmd-'`) and
`editor::ExpandAllHunkDiffs` (`cmd-"`) actions to browse git hunk diffs
in Zed

crates/editor/src/git.rs

@@ -4,6 +4,7 @@ use std::ops::Range;
 
 use git::diff::{DiffHunk, DiffHunkStatus};
 use language::Point;
+use multi_buffer::Anchor;
 
 use crate::{
     display_map::{DisplaySnapshot, ToDisplayPoint},
@@ -17,7 +18,9 @@ pub enum DisplayDiffHunk {
     },
 
     Unfolded {
+        diff_base_byte_range: Range<usize>,
         display_row_range: Range<u32>,
+        multi_buffer_range: Range<Anchor>,
         status: DiffHunkStatus,
     },
 }
@@ -45,7 +48,7 @@ impl DisplayDiffHunk {
     }
 }
 
-pub fn diff_hunk_to_display(hunk: DiffHunk<u32>, snapshot: &DisplaySnapshot) -> DisplayDiffHunk {
+pub fn diff_hunk_to_display(hunk: &DiffHunk<u32>, snapshot: &DisplaySnapshot) -> DisplayDiffHunk {
     let hunk_start_point = Point::new(hunk.associated_range.start, 0);
     let hunk_start_point_sub = Point::new(hunk.associated_range.start.saturating_sub(1), 0);
     let hunk_end_point_sub = Point::new(
@@ -81,11 +84,16 @@ pub fn diff_hunk_to_display(hunk: DiffHunk<u32>, snapshot: &DisplaySnapshot) ->
 
         let hunk_end_row = hunk.associated_range.end.max(hunk.associated_range.start);
         let hunk_end_point = Point::new(hunk_end_row, 0);
+
+        let multi_buffer_start = snapshot.buffer_snapshot.anchor_after(hunk_start_point);
+        let multi_buffer_end = snapshot.buffer_snapshot.anchor_before(hunk_end_point);
         let end = hunk_end_point.to_display_point(snapshot).row();
 
         DisplayDiffHunk::Unfolded {
             display_row_range: start..end,
+            multi_buffer_range: multi_buffer_start..multi_buffer_end,
             status: hunk.status(),
+            diff_base_byte_range: hunk.diff_base_byte_range.clone(),
         }
     }
 }