A diff reads as the code it changes: hunks in their file's language, added and removed rows tinted

A .diff or .patch pane, and a command pane whose output is a diff (`git
diff`, `git show`, `diff -u`; told by a `diff --git` line, or `---`/`+++`
with a `@@` under them, in its first rows), colour each hunk's code in the
language of the file its section names (`+++ b/<path>`, `--- a/<path>` for
a deleted file), with tree-sitter, as highlightLocations does for results.

src/diff.zig walks a unified diff by its `@@` counts, so a removed line
that reads `--- x` is no header. Each side of a hunk is parsed as one text
(context and removed lines the old side, context and added lines the new),
so a string or comment across lines colours as it does in the file; a side
no line takes its colours from is not parsed. A section's hunks share a
parse, in pieces of about 40 lines (a hunk past 80 is cut), only those in
view, and each piece's colours are kept by its bytes, so scrolling back and
a terminal's every repaint parse nothing again.

Added and removed lines carry a flag in their style byte; the painter tints
their rows to the pane's edge, a little way from the page toward the
theme's ANSI green or red, and draws the prefix in that hue pushed to read
on it. A file in no known language keeps the old line colours.

A command pane is read once its command has finished: its rows are copied
once (File.DiffOutput, dropped when the pane runs again), so no frame dumps
the scrollback, and painted over what git printed. A running command is
shown as it prints.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/pardes.zig b/src/pardes.zig
index b16d39b7..9fe6a1fb 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -4502,6 +4502,9 @@ pub const Pardes = struct {
     /// the terminal motion surface, memoized against the pane it was built
     /// for — see panes.terminal.RowsCache for the lifetime rule
     shell_rows: panes.terminal.RowsCache = .{},
+    /// Finished command panes' output, and whether it is a diff
+    /// (File.DiffOutput).
+    diff_output: panes.File.DiffOutput = .{},
 
     /// The message row's entry points, called from everywhere as
     /// `p.setMessage(...)`; they live with the rest of it in Messages.zig.
@@ -4752,6 +4755,7 @@ pub const Pardes = struct {
         p.locations_cache.deinit(p.tree_sitter_gpa);
         p.fs.deinit(gpa);
         p.shell_rows.reset(gpa);
+        p.diff_output.reset(gpa);
         p.scratch.deinit();
         p.frame_arena.deinit();
         gpa.free(p.surface.cells);