core: text line diff, unified output and bench-diff

build/app.zig

@@ -841,7 +841,7 @@ pub fn construct(b: *std.Build, target: std.Build.ResolvedTarget, optimize: std.
         // A document state as the bytes that differ from another: how a track's checkpoints
         // stay small. std-only (see state_delta.zig); `Tracks` keeps its checkpoints with it.
         .{ "fizzy-state-delta-tests", "app/state_delta.zig" },
-        // Image diff: RGBA8 rows and tiles to the rects that differ. std-only (see
+        // Image diff (RGBA8 to rects) and text diff (histogram lines, unified output). std-only (see
         // core/diff.zig); `bench-diff` measures it.
         .{ "fizzy-diff-tests", "core/diff.zig" },
         // When a document's transport shows and for how long, how far a held undo goes, which
@@ -1507,7 +1507,7 @@ pub fn construct(b: *std.Build, target: std.Build.ResolvedTarget, optimize: std.
         bench_step.dependOn(&run_bench.step);
     }
 
-    // `zig build bench-diff` — core.diff on a 4K image and a 2048x2048 sprite of 50 layers (prints
+    // `zig build bench-diff` — core.diff on a 4K image, a 2048x2048 sprite of 50 layers and 1 MB of text (prints
     // timings). Same rules as `bench-tape`; std-only, so it needs no window.
     {
         const bench_module = b.createModule(.{
@@ -1522,7 +1522,7 @@ pub fn construct(b: *std.Build, target: std.Build.ResolvedTarget, optimize: std.
         }));
         const bench_diff = b.addTest(.{ .name = "fizzy-bench-diff", .root_module = bench_module });
 
-        const bench_step = b.step("bench-diff", "Benchmark core.diff: a 4K image, a 50-layer sprite (prints timings)");
+        const bench_step = b.step("bench-diff", "Benchmark core.diff: a 4K image, a 50-layer sprite, 1 MB of text (prints timings)");
         const run_bench = b.addRunArtifact(bench_diff);
         run_bench.has_side_effects = true;
         bench_step.dependOn(&run_bench.step);

core/core.zig

@@ -106,7 +106,7 @@ pub const lsp = @import("lsp/lsp.zig");
 /// lower scores are better.
 pub const fuzzy = @import("fuzzy.zig");
 
-/// Std-only diffing (images so far): which regions of a document's state differ. See `diff.zig`.
+/// Std-only diffing (images and text): which regions of a document's state differ. See `diff.zig`.
 pub const diff = @import("diff.zig");
 
 /// The project's file set: one cached, searchable view of what is on disk, owned by the host and

core/diff.zig

@@ -6,8 +6,15 @@
 pub const Image = @import("diff/Image.zig");
 /// A keepable per-tile hash of an image, 8 bytes per tile, to diff a past state against.
 pub const TileGrid = @import("diff/TileGrid.zig");
+/// A line diff of two texts: histogram with a Myers fallback, over a reusable scratch.
+pub const Text = @import("diff/Text.zig");
+/// A text diff's hunks as a standard unified diff, with a size cap.
+pub const unified = @import("diff/unified.zig");
 
 test {
     _ = Image;
     _ = TileGrid;
+    _ = Text;
+    _ = unified;
+    _ = @import("diff/tests.zig");
 }