Add the ability to propose changes to a set of buffers (#18170)

This PR introduces functionality for creating *branches* of buffers that
can be used to preview and edit change sets that haven't yet been
applied to the buffers themselves.

Release Notes:

- N/A

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>
Co-authored-by: Marshall <marshall@zed.dev>

crates/editor/src/editor.rs

@@ -35,6 +35,7 @@ mod lsp_ext;
 mod mouse_context_menu;
 pub mod movement;
 mod persistence;
+mod proposed_changes_editor;
 mod rust_analyzer_ext;
 pub mod scroll;
 mod selections_collection;
@@ -46,7 +47,7 @@ mod signature_help;
 #[cfg(any(test, feature = "test-support"))]
 pub mod test;
 
-use ::git::diff::{DiffHunk, DiffHunkStatus};
+use ::git::diff::DiffHunkStatus;
 use ::git::{parse_git_remote_url, BuildPermalinkParams, GitHostingProviderRegistry};
 pub(crate) use actions::*;
 use aho_corasick::AhoCorasick;
@@ -98,6 +99,7 @@ use language::{
 };
 use language::{point_to_lsp, BufferRow, CharClassifier, Runnable, RunnableRange};
 use linked_editing_ranges::refresh_linked_ranges;
+use proposed_changes_editor::{ProposedChangesBuffer, ProposedChangesEditor};
 use similar::{ChangeTag, TextDiff};
 use task::{ResolvedTask, TaskTemplate, TaskVariables};
 
@@ -113,7 +115,9 @@ pub use multi_buffer::{
     Anchor, AnchorRangeExt, ExcerptId, ExcerptRange, MultiBuffer, MultiBufferSnapshot, ToOffset,
     ToPoint,
 };
-use multi_buffer::{ExpandExcerptDirection, MultiBufferPoint, MultiBufferRow, ToOffsetUtf16};
+use multi_buffer::{
+    ExpandExcerptDirection, MultiBufferDiffHunk, MultiBufferPoint, MultiBufferRow, ToOffsetUtf16,
+};
 use ordered_float::OrderedFloat;
 use parking_lot::{Mutex, RwLock};
 use project::project_settings::{GitGutterSetting, ProjectSettings};
@@ -6152,7 +6156,7 @@ impl Editor {
     pub fn prepare_revert_change(
         revert_changes: &mut HashMap<BufferId, Vec<(Range<text::Anchor>, Rope)>>,
         multi_buffer: &Model<MultiBuffer>,
-        hunk: &DiffHunk<MultiBufferRow>,
+        hunk: &MultiBufferDiffHunk,
         cx: &AppContext,
     ) -> Option<()> {
         let buffer = multi_buffer.read(cx).buffer(hunk.buffer_id)?;
@@ -9338,7 +9342,7 @@ impl Editor {
         snapshot: &DisplaySnapshot,
         initial_point: Point,
         is_wrapped: bool,
-        hunks: impl Iterator<Item = DiffHunk<MultiBufferRow>>,
+        hunks: impl Iterator<Item = MultiBufferDiffHunk>,
         cx: &mut ViewContext<Editor>,
     ) -> bool {
         let display_point = initial_point.to_display_point(snapshot);
@@ -11885,6 +11889,52 @@ impl Editor {
         self.searchable
     }
 
+    fn open_proposed_changes_editor(
+        &mut self,
+        _: &OpenProposedChangesEditor,
+        cx: &mut ViewContext<Self>,
+    ) {
+        let Some(workspace) = self.workspace() else {
+            cx.propagate();
+            return;
+        };
+
+        let buffer = self.buffer.read(cx);
+        let mut new_selections_by_buffer = HashMap::default();
+        for selection in self.selections.all::<usize>(cx) {
+            for (buffer, mut range, _) in
+                buffer.range_to_buffer_ranges(selection.start..selection.end, cx)
+            {
+                if selection.reversed {
+                    mem::swap(&mut range.start, &mut range.end);
+                }
+                let mut range = range.to_point(buffer.read(cx));
+                range.start.column = 0;
+                range.end.column = buffer.read(cx).line_len(range.end.row);
+                new_selections_by_buffer
+                    .entry(buffer)
+                    .or_insert(Vec::new())
+                    .push(range)
+            }
+        }
+
+        let proposed_changes_buffers = new_selections_by_buffer
+            .into_iter()
+            .map(|(buffer, ranges)| ProposedChangesBuffer { buffer, ranges })
+            .collect::<Vec<_>>();
+        let proposed_changes_editor = cx.new_view(|cx| {
+            ProposedChangesEditor::new(proposed_changes_buffers, self.project.clone(), cx)
+        });
+
+        cx.window_context().defer(move |cx| {
+            workspace.update(cx, |workspace, cx| {
+                workspace.active_pane().update(cx, |pane, cx| {
+                    pane.add_item(Box::new(proposed_changes_editor), true, true, None, cx);
+                });
+            });
+        });
+    }
+
     fn open_excerpts_in_split(&mut self, _: &OpenExcerptsSplit, cx: &mut ViewContext<Self>) {
         self.open_excerpts_common(true, cx)
     }
@@ -12399,7 +12449,7 @@ impl Editor {
 fn hunks_for_selections(
     multi_buffer_snapshot: &MultiBufferSnapshot,
     selections: &[Selection<Anchor>],
-) -> Vec<DiffHunk<MultiBufferRow>> {
+) -> Vec<MultiBufferDiffHunk> {
     let buffer_rows_for_selections = selections.iter().map(|selection| {
         let head = selection.head();
         let tail = selection.tail();
@@ -12418,7 +12468,7 @@ fn hunks_for_selections(
 pub fn hunks_for_rows(
     rows: impl Iterator<Item = Range<MultiBufferRow>>,
     multi_buffer_snapshot: &MultiBufferSnapshot,
-) -> Vec<DiffHunk<MultiBufferRow>> {
+) -> Vec<MultiBufferDiffHunk> {
     let mut hunks = Vec::new();
     let mut processed_buffer_rows: HashMap<BufferId, HashSet<Range<text::Anchor>>> =
         HashMap::default();
@@ -12430,14 +12480,14 @@ pub fn hunks_for_rows(
             // when the caret is just above or just below the deleted hunk.
             let allow_adjacent = hunk_status(&hunk) == DiffHunkStatus::Removed;
             let related_to_selection = if allow_adjacent {
-                hunk.associated_range.overlaps(&query_rows)
-                    || hunk.associated_range.start == query_rows.end
-                    || hunk.associated_range.end == query_rows.start
+                hunk.row_range.overlaps(&query_rows)
+                    || hunk.row_range.start == query_rows.end
+                    || hunk.row_range.end == query_rows.start
             } else {
                 // `selected_multi_buffer_rows` are inclusive (e.g. [2..2] means 2nd row is selected)
-                // `hunk.associated_range` is exclusive (e.g. [2..3] means 2nd row is selected)
-                hunk.associated_range.overlaps(&selected_multi_buffer_rows)
-                    || selected_multi_buffer_rows.end == hunk.associated_range.start
+                // `hunk.row_range` is exclusive (e.g. [2..3] means 2nd row is selected)
+                hunk.row_range.overlaps(&selected_multi_buffer_rows)
+                    || selected_multi_buffer_rows.end == hunk.row_range.start
             };
             if related_to_selection {
                 if !processed_buffer_rows
@@ -13738,10 +13788,10 @@ impl RowRangeExt for Range<DisplayRow> {
     }
 }
 
-fn hunk_status(hunk: &DiffHunk<MultiBufferRow>) -> DiffHunkStatus {
+fn hunk_status(hunk: &MultiBufferDiffHunk) -> DiffHunkStatus {
     if hunk.diff_base_byte_range.is_empty() {
         DiffHunkStatus::Added
-    } else if hunk.associated_range.is_empty() {
+    } else if hunk.row_range.is_empty() {
         DiffHunkStatus::Removed
     } else {
         DiffHunkStatus::Modified