Show (git) diff signs in gutter (#3890)

* Show (git) diff signs in gutter (#3890)

Avoid string allocation when git diffing

Incrementally diff using changesets

refactor diffs to be provider indepndent and improve git implementation

remove dependency on zlib-ng

switch to asynchronus diffing with similar

Update helix-vcs/Cargo.toml

fix toml formatting

Co-authored-by: Ivan Tham <pickfire@riseup.net>

fix typo in documentation

use ropey reexpors from helix-core

fix crash when creating new file

remove useless use if io::Cursor

fix spelling mistakes

implement suggested improvement to repository loading

improve git test isolation

remove lefover comments

Co-authored-by: univerz <univerz@fu-solution.com>

fixed spelling mistake

minor cosmetic changes

fix: set self.differ to None if decoding the diff_base fails

fixup formatting

Co-authored-by: Ivan Tham <pickfire@riseup.net>

reload diff_base when file is reloaded from disk

switch to imara-diff

Fixup formatting

Co-authored-by: Blaž Hrastnik <blaz@mxxn.io>

Redraw buffer whenever a diff is updated.

Only store hunks instead of changes for individual lines to easily allow
jumping between them

Update to latest gitoxide version

Change default diff gutter position

Only update gutter after timeout

* update diff gutter synchronously, with a timeout

* Apply suggestions from code review

Co-authored-by: Blaž Hrastnik <blaz@mxxn.io>
Co-authored-by: Michael Davis <mcarsondavis@gmail.com>

* address review comments and ensure lock is always aquired

* remove configuration for redraw timeout

Co-authored-by: Blaž Hrastnik <blaz@mxxn.io>
Co-authored-by: Michael Davis <mcarsondavis@gmail.com>

1 files changed, 52 insertions, 3 deletions

diff --git a/helix-view/src/gutter.rs b/helix-view/src/gutter.rs
index 61a17791..377518fb 100644
--- a/helix-view/src/gutter.rs
+++ b/helix-view/src/gutter.rs
@@ -12,7 +12,7 @@ fn count_digits(n: usize) -> usize {
     std::iter::successors(Some(n), |&n| (n >= 10).then(|| n / 10)).count()
 }
 
-pub type GutterFn<'doc> = Box<dyn Fn(usize, bool, &mut String) -> Option<Style> + 'doc>;
+pub type GutterFn<'doc> = Box<dyn FnMut(usize, bool, &mut String) -> Option<Style> + 'doc>;
 pub type Gutter =
     for<'doc> fn(&'doc Editor, &'doc Document, &View, &Theme, bool, usize) -> GutterFn<'doc>;
 
@@ -31,6 +31,7 @@ impl GutterType {
             }
             GutterType::LineNumbers => line_numbers(editor, doc, view, theme, is_focused),
             GutterType::Spacer => padding(editor, doc, view, theme, is_focused),
+            GutterType::Diff => diff(editor, doc, view, theme, is_focused),
         }
     }
 
@@ -39,6 +40,7 @@ impl GutterType {
             GutterType::Diagnostics => 1,
             GutterType::LineNumbers => line_numbers_width(_view, doc),
             GutterType::Spacer => 1,
+            GutterType::Diff => 1,
         }
     }
 }
@@ -83,6 +85,53 @@ pub fn diagnostic<'doc>(
     })
 }
 
+pub fn diff<'doc>(
+    _editor: &'doc Editor,
+    doc: &'doc Document,
+    _view: &View,
+    theme: &Theme,
+    _is_focused: bool,
+) -> GutterFn<'doc> {
+    let added = theme.get("diff.plus");
+    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 mut hunk_i = 0;
+        let mut hunk = hunks.nth_hunk(hunk_i);
+        Box::new(move |line: usize, _selected: bool, out: &mut String| {
+            // truncating the line is fine here because we don't compute diffs
+            // for files with more lines than i32::MAX anyways
+            // we need to special case removals here
+            // these technically do not have a range of lines to highlight (`hunk.after.start == hunk.after.end`).
+            // However we still want to display these hunks correctly we must not yet skip to the next hunk here
+            while hunk.after.end < line as u32
+                || !hunk.is_pure_removal() && line as u32 == hunk.after.end
+            {
+                hunk_i += 1;
+                hunk = hunks.nth_hunk(hunk_i);
+            }
+
+            if hunk.after.start > line as u32 {
+                return None;
+            }
+
+            let (icon, style) = if hunk.is_pure_insertion() {
+                ("▍", added)
+            } else if hunk.is_pure_removal() {
+                ("▔", deleted)
+            } else {
+                ("▍", modified)
+            };
+
+            write!(out, "{}", icon).unwrap();
+            Some(style)
+        })
+    } else {
+        Box::new(move |_, _, _| None)
+    }
+}
+
 pub fn line_numbers<'doc>(
     editor: &'doc Editor,
     doc: &'doc Document,
@@ -226,8 +275,8 @@ pub fn diagnostics_or_breakpoints<'doc>(
     theme: &Theme,
     is_focused: bool,
 ) -> GutterFn<'doc> {
-    let diagnostics = diagnostic(editor, doc, view, theme, is_focused);
-    let breakpoints = breakpoints(editor, doc, view, theme, is_focused);
+    let mut diagnostics = diagnostic(editor, doc, view, theme, is_focused);
+    let mut breakpoints = breakpoints(editor, doc, view, theme, is_focused);
 
     Box::new(move |line, selected, out| {
         breakpoints(line, selected, out).or_else(|| diagnostics(line, selected, out))