Add command for resetting diff hunks (#5736)

8 files changed, 140 insertions, 37 deletions

diff --git a/book/src/generated/typable-cmd.md b/book/src/generated/typable-cmd.md
index badadc43..8b367aad 100644
--- a/book/src/generated/typable-cmd.md
+++ b/book/src/generated/typable-cmd.md
@@ -76,3 +76,4 @@
 | `:pipe` | Pipe each selection to the shell command. |
 | `:pipe-to` | Pipe each selection to the shell command, ignoring output. |
 | `:run-shell-command`, `:sh` | Run a shell command |
+| `:reset-diff-change`, `:diffget`, `:diffg` | Reset the diff change at the cursor position. |
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index c76e9f2b..ebdfdfde 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -3011,13 +3011,13 @@ fn goto_first_change_impl(cx: &mut Context, reverse: bool) {
     let (view, doc) = current!(editor);
     if let Some(handle) = doc.diff_handle() {
         let hunk = {
-            let hunks = handle.hunks();
+            let diff = handle.load();
             let idx = if reverse {
-                hunks.len().saturating_sub(1)
+                diff.len().saturating_sub(1)
             } else {
                 0
             };
-            hunks.nth_hunk(idx)
+            diff.nth_hunk(idx)
         };
         if hunk != Hunk::NONE {
             let range = hunk_range(hunk, doc.text().slice(..));
@@ -3049,19 +3049,19 @@ fn goto_next_change_impl(cx: &mut Context, direction: Direction) {
         let selection = doc.selection(view.id).clone().transform(|range| {
             let cursor_line = range.cursor_line(doc_text) as u32;
 
-            let hunks = diff_handle.hunks();
+            let diff = diff_handle.load();
             let hunk_idx = match direction {
-                Direction::Forward => hunks
+                Direction::Forward => diff
                     .next_hunk(cursor_line)
-                    .map(|idx| (idx + count).min(hunks.len() - 1)),
-                Direction::Backward => hunks
+                    .map(|idx| (idx + count).min(diff.len() - 1)),
+                Direction::Backward => diff
                     .prev_hunk(cursor_line)
                     .map(|idx| idx.saturating_sub(count)),
             };
             let Some(hunk_idx) = hunk_idx else {
                 return range;
             };
-            let hunk = hunks.nth_hunk(hunk_idx);
+            let hunk = diff.nth_hunk(hunk_idx);
             let new_range = hunk_range(hunk, doc_text);
             if editor.mode == Mode::Select {
                 let head = if new_range.head < range.anchor {
@@ -4721,14 +4721,14 @@ fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
 
                 let textobject_change = |range: Range| -> Range {
                     let diff_handle = doc.diff_handle().unwrap();
-                    let hunks = diff_handle.hunks();
+                    let diff = diff_handle.load();
                     let line = range.cursor_line(text);
-                    let hunk_idx = if let Some(hunk_idx) = hunks.hunk_at(line as u32, false) {
+                    let hunk_idx = if let Some(hunk_idx) = diff.hunk_at(line as u32, false) {
                         hunk_idx
                     } else {
                         return range;
                     };
-                    let hunk = hunks.nth_hunk(hunk_idx).after;
+                    let hunk = diff.nth_hunk(hunk_idx).after;
 
                     let start = text.line_to_char(hunk.start as usize);
                     let end = text.line_to_char(hunk.end as usize);
diff --git a/helix-term/src/commands/typed.rs b/helix-term/src/commands/typed.rs
index 0ddca6df..77c14321 100644
--- a/helix-term/src/commands/typed.rs
+++ b/helix-term/src/commands/typed.rs
@@ -2033,6 +2033,64 @@ fn run_shell_command(
     Ok(())
 }
 
+fn reset_diff_change(
+    cx: &mut compositor::Context,
+    args: &[Cow<str>],
+    event: PromptEvent,
+) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+    ensure!(args.is_empty(), ":reset-diff-change takes no arguments");
+
+    let editor = &mut cx.editor;
+    let scrolloff = editor.config().scrolloff;
+
+    let (view, doc) = current!(editor);
+    // TODO refactor to use let..else once MSRV is raised to 1.65
+    let handle = match doc.diff_handle() {
+        Some(handle) => handle,
+        None => bail!("Diff is not available in the current buffer"),
+    };
+
+    let diff = handle.load();
+    let doc_text = doc.text().slice(..);
+    let line = doc.selection(view.id).primary().cursor_line(doc_text);
+
+    // TODO refactor to use let..else once MSRV is raised to 1.65
+    let hunk_idx = match diff.hunk_at(line as u32, true) {
+        Some(hunk_idx) => hunk_idx,
+        None => bail!("There is no change at the cursor"),
+    };
+    let hunk = diff.nth_hunk(hunk_idx);
+    let diff_base = diff.diff_base();
+    let before_start = diff_base.line_to_char(hunk.before.start as usize);
+    let before_end = diff_base.line_to_char(hunk.before.end as usize);
+    let text: Tendril = diff
+        .diff_base()
+        .slice(before_start..before_end)
+        .chunks()
+        .collect();
+    let anchor = doc_text.line_to_char(hunk.after.start as usize);
+    let transaction = Transaction::change(
+        doc.text(),
+        [(
+            anchor,
+            doc_text.line_to_char(hunk.after.end as usize),
+            (!text.is_empty()).then_some(text),
+        )]
+        .into_iter(),
+    );
+    drop(diff); // make borrow check happy
+    doc.apply(&transaction, view.id);
+    // select inserted text
+    let text_len = before_end - before_start;
+    doc.set_selection(view.id, Selection::single(anchor, anchor + text_len));
+    doc.append_changes_to_history(view);
+    view.ensure_cursor_in_view(doc, scrolloff);
+    Ok(())
+}
+
 pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
         TypableCommand {
             name: "quit",
@@ -2569,6 +2627,13 @@ pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
             fun: run_shell_command,
             completer: Some(completers::filename),
         },
+       TypableCommand {
+            name: "reset-diff-change",
+            aliases: &["diffget", "diffg"],
+            doc: "Reset the diff change at the cursor position.",
+            fun: reset_diff_change,
+            completer: None,
+        },
     ];
 
 pub static TYPABLE_COMMAND_MAP: Lazy<HashMap<&'static str, &'static TypableCommand>> =
diff --git a/helix-vcs/src/diff.rs b/helix-vcs/src/diff.rs
index 9c6a362f..ca33dda4 100644
--- a/helix-vcs/src/diff.rs
+++ b/helix-vcs/src/diff.rs
@@ -28,11 +28,18 @@ struct Event {
     render_lock: Option<RenderLock>,
 }
 
+#[derive(Clone, Debug, Default)]
+struct DiffInner {
+    diff_base: Rope,
+    doc: Rope,
+    hunks: Vec<Hunk>,
+}
+
 #[derive(Clone, Debug)]
 pub struct DiffHandle {
     channel: UnboundedSender<Event>,
     render_lock: Arc<RwLock<()>>,
-    hunks: Arc<Mutex<Vec<Hunk>>>,
+    diff: Arc<Mutex<DiffInner>>,
     inverted: bool,
 }
 
@@ -47,10 +54,10 @@ impl DiffHandle {
         redraw_handle: RedrawHandle,
     ) -> (DiffHandle, JoinHandle<()>) {
         let (sender, receiver) = unbounded_channel();
-        let hunks: Arc<Mutex<Vec<Hunk>>> = Arc::default();
+        let diff: Arc<Mutex<DiffInner>> = Arc::default();
         let worker = DiffWorker {
             channel: receiver,
-            hunks: hunks.clone(),
+            diff: diff.clone(),
             new_hunks: Vec::default(),
             redraw_notify: redraw_handle.0,
             diff_finished_notify: Arc::default(),
@@ -58,7 +65,7 @@ impl DiffHandle {
         let handle = tokio::spawn(worker.run(diff_base, doc));
         let differ = DiffHandle {
             channel: sender,
-            hunks,
+            diff,
             inverted: false,
             render_lock: redraw_handle.1,
         };
@@ -69,9 +76,9 @@ impl DiffHandle {
         self.inverted = !self.inverted;
     }
 
-    pub fn hunks(&self) -> FileHunks {
-        FileHunks {
-            hunks: self.hunks.lock(),
+    pub fn load(&self) -> Diff {
+        Diff {
+            diff: self.diff.lock(),
             inverted: self.inverted,
         }
     }
@@ -168,12 +175,28 @@ impl Hunk {
 /// A list of changes in a file sorted in ascending
 /// non-overlapping order
 #[derive(Debug)]
-pub struct FileHunks<'a> {
-    hunks: MutexGuard<'a, Vec<Hunk>>,
+pub struct Diff<'a> {
+    diff: MutexGuard<'a, DiffInner>,
     inverted: bool,
 }
 
-impl FileHunks<'_> {
+impl Diff<'_> {
+    pub fn diff_base(&self) -> &Rope {
+        if self.inverted {
+            &self.diff.doc
+        } else {
+            &self.diff.diff_base
+        }
+    }
+
+    pub fn doc(&self) -> &Rope {
+        if self.inverted {
+            &self.diff.diff_base
+        } else {
+            &self.diff.doc
+        }
+    }
+
     pub fn is_inverted(&self) -> bool {
         self.inverted
     }
@@ -181,7 +204,7 @@ impl FileHunks<'_> {
     /// Returns the `Hunk` for the `n`th change in this file.
     /// if there is no `n`th change  `Hunk::NONE` is returned instead.
     pub fn nth_hunk(&self, n: u32) -> Hunk {
-        match self.hunks.get(n as usize) {
+        match self.diff.hunks.get(n as usize) {
             Some(hunk) if self.inverted => hunk.invert(),
             Some(hunk) => hunk.clone(),
             None => Hunk::NONE,
@@ -189,7 +212,7 @@ impl FileHunks<'_> {
     }
 
     pub fn len(&self) -> u32 {
-        self.hunks.len() as u32
+        self.diff.hunks.len() as u32
     }
 
     pub fn is_empty(&self) -> bool {
@@ -204,19 +227,20 @@ impl FileHunks<'_> {
         };
 
         let res = self
+            .diff
             .hunks
             .binary_search_by_key(&line, |hunk| hunk_range(hunk).start);
 
         match res {
             // Search found a hunk that starts exactly at this line, return the next hunk if it exists.
-            Ok(pos) if pos + 1 == self.hunks.len() => None,
+            Ok(pos) if pos + 1 == self.diff.hunks.len() => None,
             Ok(pos) => Some(pos as u32 + 1),
 
             // No hunk starts exactly at this line, so the search returns
             // the position where a hunk starting at this line should be inserted.
             // That position is exactly the position of the next hunk or the end
             // of the list if no such hunk exists
-            Err(pos) if pos == self.hunks.len() => None,
+            Err(pos) if pos == self.diff.hunks.len() => None,
             Err(pos) => Some(pos as u32),
         }
     }
@@ -228,6 +252,7 @@ impl FileHunks<'_> {
             |hunk: &Hunk| hunk.after.clone()
         };
         let res = self
+            .diff
             .hunks
             .binary_search_by_key(&line, |hunk| hunk_range(hunk).end);
 
@@ -237,7 +262,7 @@ impl FileHunks<'_> {
             // which represents a pure removal.
             // Removals are technically empty but are still shown as single line hunks
             // and as such we must jump to the previous hunk (if it exists) if we are already inside the removal
-            Ok(pos) if !hunk_range(&self.hunks[pos]).is_empty() => Some(pos as u32),
+            Ok(pos) if !hunk_range(&self.diff.hunks[pos]).is_empty() => Some(pos as u32),
 
             // No hunk ends exactly at this line, so the search returns
             // the position where a hunk ending at this line should be inserted.
@@ -255,6 +280,7 @@ impl FileHunks<'_> {
         };
 
         let res = self
+            .diff
             .hunks
             .binary_search_by_key(&line, |hunk| hunk_range(hunk).start);
 
@@ -267,7 +293,7 @@ impl FileHunks<'_> {
             // The previous hunk contains this hunk if it exists and doesn't end before this line
             Err(0) => None,
             Err(pos) => {
-                let hunk = hunk_range(&self.hunks[pos - 1]);
+                let hunk = hunk_range(&self.diff.hunks[pos - 1]);
                 if hunk.end > line || include_removal && hunk.start == line && hunk.is_empty() {
                     Some(pos as u32 - 1)
                 } else {
diff --git a/helix-vcs/src/diff/line_cache.rs b/helix-vcs/src/diff/line_cache.rs
index c3ee5daa..8e48250f 100644
--- a/helix-vcs/src/diff/line_cache.rs
+++ b/helix-vcs/src/diff/line_cache.rs
@@ -43,6 +43,14 @@ impl InternedRopeLines {
         res
     }
 
+    pub fn doc(&self) -> Rope {
+        self.doc.clone()
+    }
+
+    pub fn diff_base(&self) -> Rope {
+        self.diff_base.clone()
+    }
+
     /// Updates the `diff_base` and optionally the document if `doc` is not None
     pub fn update_diff_base(&mut self, diff_base: Rope, doc: Option<Rope>) {
         self.interned.clear();
diff --git a/helix-vcs/src/diff/worker.rs b/helix-vcs/src/diff/worker.rs
index f4bb4dbf..5406446f 100644
--- a/helix-vcs/src/diff/worker.rs
+++ b/helix-vcs/src/diff/worker.rs
@@ -10,7 +10,7 @@ use tokio::sync::Notify;
 use tokio::time::{timeout, timeout_at, Duration};
 
 use crate::diff::{
-    Event, RenderLock, ALGORITHM, DIFF_DEBOUNCE_TIME_ASYNC, DIFF_DEBOUNCE_TIME_SYNC,
+    DiffInner, Event, RenderLock, ALGORITHM, DIFF_DEBOUNCE_TIME_ASYNC, DIFF_DEBOUNCE_TIME_SYNC,
 };
 
 use super::line_cache::InternedRopeLines;
@@ -21,7 +21,7 @@ mod test;
 
 pub(super) struct DiffWorker {
     pub channel: UnboundedReceiver<Event>,
-    pub hunks: Arc<Mutex<Vec<Hunk>>>,
+    pub diff: Arc<Mutex<DiffInner>>,
     pub new_hunks: Vec<Hunk>,
     pub redraw_notify: Arc<Notify>,
     pub diff_finished_notify: Arc<Notify>,
@@ -46,7 +46,7 @@ impl DiffWorker {
         if let Some(lines) = interner.interned_lines() {
             self.perform_diff(lines);
         }
-        self.apply_hunks();
+        self.apply_hunks(interner.diff_base(), interner.doc());
         while let Some(event) = self.channel.recv().await {
             let (doc, diff_base) = self.accumulate_events(event).await;
 
@@ -70,15 +70,18 @@ impl DiffWorker {
             #[cfg(not(test))]
             tokio::task::block_in_place(process_accumulated_events);
 
-            self.apply_hunks();
+            self.apply_hunks(interner.diff_base(), interner.doc());
         }
     }
 
     /// update the hunks (used by the gutter) by replacing it with `self.new_hunks`.
     /// `self.new_hunks` is always empty after this function runs.
     /// To improve performance this function tries to reuse the allocation of the old diff previously stored in `self.line_diffs`
-    fn apply_hunks(&mut self) {
-        swap(&mut *self.hunks.lock(), &mut self.new_hunks);
+    fn apply_hunks(&mut self, diff_base: Rope, doc: Rope) {
+        let mut diff = self.diff.lock();
+        diff.diff_base = diff_base;
+        diff.doc = doc;
+        swap(&mut diff.hunks, &mut self.new_hunks);
         self.diff_finished_notify.notify_waiters();
         self.new_hunks.clear();
     }
diff --git a/helix-vcs/src/diff/worker/test.rs b/helix-vcs/src/diff/worker/test.rs
index 14442426..6a68d987 100644
--- a/helix-vcs/src/diff/worker/test.rs
+++ b/helix-vcs/src/diff/worker/test.rs
@@ -12,12 +12,12 @@ impl DiffHandle {
         )
     }
     async fn into_diff(self, handle: JoinHandle<()>) -> Vec<Hunk> {
-        let hunks = self.hunks;
+        let diff = self.diff;
         // dropping the channel terminates the task
         drop(self.channel);
         handle.await.unwrap();
-        let hunks = hunks.lock();
-        Vec::clone(&*hunks)
+        let diff = diff.lock();
+        Vec::clone(&diff.hunks)
     }
 }
 
diff --git a/helix-view/src/gutter.rs b/helix-view/src/gutter.rs
index cb9e4333..36e8e16a 100644
--- a/helix-view/src/gutter.rs
+++ b/helix-view/src/gutter.rs
@@ -100,7 +100,7 @@ pub fn diff<'doc>(
     let deleted = theme.get("diff.minus");
     let modified = theme.get("diff.delta");
     if let Some(diff_handle) = doc.diff_handle() {
-        let hunks = diff_handle.hunks();
+        let hunks = diff_handle.load();
         let mut hunk_i = 0;
         let mut hunk = hunks.nth_hunk(hunk_i);
         Box::new(