refactor(snapshot): store unified patches in file diffs (#21244)

Co-authored-by: Adam <2363879+adamdotdevin@users.noreply.github.com>

packages/opencode/src/project/vcs.ts

@@ -1,4 +1,5 @@
 import { Effect, Layer, ServiceMap, Stream } from "effect"
+import { formatPatch, structuredPatch } from "diff"
 import path from "path"
 import { Bus } from "@/bus"
 import { BusEvent } from "@/bus/bus-event"
@@ -7,7 +8,6 @@ import { makeRuntime } from "@/effect/run-service"
 import { AppFileSystem } from "@/filesystem"
 import { FileWatcher } from "@/file/watcher"
 import { Git } from "@/git"
-import { Snapshot } from "@/snapshot"
 import { Log } from "@/util/log"
 import { Instance } from "./instance"
 import z from "zod"
@@ -49,6 +49,8 @@ export namespace Vcs {
     map: Map<string, { additions: number; deletions: number }>,
   ) {
     const base = ref ? yield* git.prefix(cwd) : ""
+    const patch = (file: string, before: string, after: string) =>
+      formatPatch(structuredPatch(file, file, before, after, "", "", { context: Number.MAX_SAFE_INTEGER }))
     const next = yield* Effect.forEach(
       list,
       (item) =>
@@ -58,12 +60,11 @@ export namespace Vcs {
           const stat = map.get(item.file)
           return {
             file: item.file,
-            before,
-            after,
+            patch: patch(item.file, before, after),
             additions: stat?.additions ?? (item.status === "added" ? count(after) : 0),
             deletions: stat?.deletions ?? (item.status === "deleted" ? count(before) : 0),
             status: item.status,
-          } satisfies Snapshot.FileDiff
+          } satisfies FileDiff
         }),
       { concurrency: 8 },
     )
@@ -125,11 +126,24 @@ export namespace Vcs {
     })
   export type Info = z.infer<typeof Info>
 
+  export const FileDiff = z
+    .object({
+      file: z.string(),
+      patch: z.string(),
+      additions: z.number(),
+      deletions: z.number(),
+      status: z.enum(["added", "deleted", "modified"]).optional(),
+    })
+    .meta({
+      ref: "VcsFileDiff",
+    })
+  export type FileDiff = z.infer<typeof FileDiff>
+
   export interface Interface {
     readonly init: () => Effect.Effect<void>
     readonly branch: () => Effect.Effect<string | undefined>
     readonly defaultBranch: () => Effect.Effect<string | undefined>
-    readonly diff: (mode: Mode) => Effect.Effect<Snapshot.FileDiff[]>
+    readonly diff: (mode: Mode) => Effect.Effect<FileDiff[]>
   }
 
   interface State {