Reset all changes overlapped by selections in ':reset-diff-change'

This is useful for resetting multiple changes at once. For example you
might use 'maf' or even '%' to select a larger region and reset all
changes within.

The original behavior of resetting the change on the current line is
retained when the primary selection is 1-width since we look for chunks
in the line range of each selection.

helix-core/src/selection.rs

@@ -13,7 +13,7 @@ use crate::{
 };
 use helix_stdx::rope::{self, RopeSliceExt};
 use smallvec::{smallvec, SmallVec};
-use std::borrow::Cow;
+use std::{borrow::Cow, iter, slice};
 use tree_sitter::Node;
 
 /// A single selection range.
@@ -503,6 +503,16 @@ impl Selection {
         &self.ranges
     }
 
+    /// Returns an iterator over the line ranges of each range in the selection.
+    ///
+    /// Adjacent and overlapping line ranges of the [Range]s in the selection are merged.
+    pub fn line_ranges<'a>(&'a self, text: RopeSlice<'a>) -> LineRangeIter<'a> {
+        LineRangeIter {
+            ranges: self.ranges.iter().peekable(),
+            text,
+        }
+    }
+
     pub fn primary_index(&self) -> usize {
         self.primary_index
     }
@@ -727,6 +737,33 @@ impl From<Range> for Selection {
     }
 }
 
+pub struct LineRangeIter<'a> {
+    ranges: iter::Peekable<slice::Iter<'a, Range>>,
+    text: RopeSlice<'a>,
+}
+
+impl<'a> Iterator for LineRangeIter<'a> {
+    type Item = (usize, usize);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let (start, mut end) = self.ranges.next()?.line_range(self.text);
+        while let Some((next_start, next_end)) =
+            self.ranges.peek().map(|range| range.line_range(self.text))
+        {
+            // Merge overlapping and adjacent ranges.
+            // This subtraction cannot underflow because the ranges are sorted.
+            if next_start - end <= 1 {
+                end = next_end;
+                self.ranges.next();
+            } else {
+                break;
+            }
+        }
+
+        Some((start, end))
+    }
+}
+
 // TODO: checkSelection -> check if valid for doc length && sorted
 
 pub fn keep_or_remove_matches(
@@ -1165,6 +1202,32 @@ mod test {
         assert_eq!(Range::new(12, 0).line_range(s), (0, 2));
     }
 
+    #[test]
+    fn selection_line_ranges() {
+        let (text, selection) = crate::test::print(
+            r#"                                           L0
+            #[|these]# line #(|ranges)# are #(|merged)#   L1
+                                                          L2
+            single one-line #(|range)#                    L3
+                                                          L4
+            single #(|multiline                           L5
+            range)#                                       L6
+                                                          L7
+            these #(|multiline                            L8
+            ranges)# are #(|also                          L9
+            merged)#                                      L10
+                                                          L11
+            adjacent #(|ranges)#                          L12
+            are merged #(|the same way)#                  L13
+            "#,
+        );
+        let rope = Rope::from_str(&text);
+        assert_eq!(
+            vec![(1, 1), (3, 3), (5, 6), (8, 10), (12, 13)],
+            selection.line_ranges(rope.slice(..)).collect::<Vec<_>>(),
+        );
+    }
+
     #[test]
     fn test_cursor() {
         let r = Rope::from_str("\r\nHi\r\nthere!");

helix-term/src/commands/typed.rs

@@ -2304,37 +2304,36 @@ fn reset_diff_change(
 
     let diff = handle.load();
     let doc_text = doc.text().slice(..);
-    let line = doc.selection(view.id).primary().cursor_line(doc_text);
-
-    let Some(hunk_idx) = diff.hunk_at(line as u32, true) else {
-        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 mut changes = 0;
+
     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(),
+        diff.hunks_intersecting_line_ranges(doc.selection(view.id).line_ranges(doc_text))
+            .map(|hunk| {
+                changes += 1;
+                let start = diff_base.line_to_char(hunk.before.start as usize);
+                let end = diff_base.line_to_char(hunk.before.end as usize);
+                let text: Tendril = diff_base.slice(start..end).chunks().collect();
+                (
+                    doc_text.line_to_char(hunk.after.start as usize),
+                    doc_text.line_to_char(hunk.after.end as usize),
+                    (!text.is_empty()).then_some(text),
+                )
+            }),
     );
+    if changes == 0 {
+        bail!("There are no changes under any selection");
+    }
+
     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);
+    cx.editor.set_status(format!(
+        "Reset {changes} change{}",
+        if changes == 1 { "" } else { "s" }
+    ));
     Ok(())
 }
 

helix-vcs/src/diff.rs

@@ -1,3 +1,4 @@
+use std::iter::Peekable;
 use std::ops::Range;
 use std::sync::Arc;
 
@@ -259,6 +260,22 @@ impl Diff<'_> {
         }
     }
 
+    /// Iterates over all hunks that intersect with the given line ranges.
+    ///
+    /// Hunks are returned at most once even when intersecting with multiple of the line
+    /// ranges.
+    pub fn hunks_intersecting_line_ranges<I>(&self, line_ranges: I) -> impl Iterator<Item = &Hunk>
+    where
+        I: Iterator<Item = (usize, usize)>,
+    {
+        HunksInLineRangesIter {
+            hunks: &self.diff.hunks,
+            line_ranges: line_ranges.peekable(),
+            inverted: self.inverted,
+            cursor: 0,
+        }
+    }
+
     pub fn hunk_at(&self, line: u32, include_removal: bool) -> Option<u32> {
         let hunk_range = if self.inverted {
             |hunk: &Hunk| hunk.before.clone()
@@ -290,3 +307,42 @@ impl Diff<'_> {
         }
     }
 }
+
+pub struct HunksInLineRangesIter<'a, I: Iterator<Item = (usize, usize)>> {
+    hunks: &'a [Hunk],
+    line_ranges: Peekable<I>,
+    inverted: bool,
+    cursor: usize,
+}
+
+impl<'a, I: Iterator<Item = (usize, usize)>> Iterator for HunksInLineRangesIter<'a, I> {
+    type Item = &'a Hunk;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let hunk_range = if self.inverted {
+            |hunk: &Hunk| hunk.before.clone()
+        } else {
+            |hunk: &Hunk| hunk.after.clone()
+        };
+
+        loop {
+            let (start_line, end_line) = self.line_ranges.peek()?;
+            let hunk = self.hunks.get(self.cursor)?;
+
+            if (hunk_range(hunk).end as usize) < *start_line {
+                // If the hunk under the cursor comes before this range, jump the cursor
+                // ahead to the next hunk that overlaps with the line range.
+                self.cursor += self.hunks[self.cursor..]
+                    .partition_point(|hunk| (hunk_range(hunk).end as usize) < *start_line);
+            } else if (hunk_range(hunk).start as usize) <= *end_line {
+                // If the hunk under the cursor overlaps with this line range, emit it
+                // and move the cursor up so that the hunk cannot be emitted twice.
+                self.cursor += 1;
+                return Some(hunk);
+            } else {
+                // Otherwise, go to the next line range.
+                self.line_ranges.next();
+            }
+        }
+    }
+}