feat(vcs): publish branch updates

packages/core/src/vcs.ts

@@ -1,12 +1,16 @@
 export * as Vcs from "./vcs"
 
-import { Context, Effect, Layer } from "effect"
+import path from "path"
+import { Context, Effect, Layer, Ref, Stream } from "effect"
 import { FileDiff } from "@opencode-ai/schema/file-diff"
+import { FileSystem } from "@opencode-ai/schema/filesystem"
 import { FileStatus, Info, Mode } from "@opencode-ai/schema/vcs"
+import { VcsEvent } from "@opencode-ai/schema/vcs-event"
 import { makeLocationNode } from "@opencode-ai/util/effect/app-node"
 import { FSUtil } from "@opencode-ai/util/fs-util"
 import { Location } from "./location"
 import { AppProcess } from "@opencode-ai/util/process"
+import { Bus } from "./bus"
 import { VcsGit } from "./vcs/git"
 import { VcsHg } from "./vcs/hg"
 
@@ -39,11 +43,44 @@ const layer = Layer.effect(
     const proc = yield* AppProcess.Service
     const fs = yield* FSUtil.Service
     const location = yield* Location.Service
+    const bus = yield* Bus.Service
     const impl = adapter(proc, fs, location)
+    const git = location.vcs?.type === "git" ? location.vcs : undefined
+    const cache = git && impl ? yield* Ref.make(yield* impl.info()) : undefined
+
+    if (cache && git && impl) {
+      const store = yield* fs.realPath(git.store).pipe(Effect.catch(() => Effect.succeed(git.store)))
+      yield* bus.subscribe(FileSystem.Event.Changed).pipe(
+        Stream.filter(
+          (event) => path.basename(event.data.file) === "HEAD" && FSUtil.contains(store, event.data.file),
+        ),
+        Stream.runForEach((event) =>
+          Effect.gen(function* () {
+            const previous = yield* Ref.get(cache)
+            const next = yield* impl.info()
+            yield* Ref.set(cache, next)
+            if (previous.branch.current === next.branch.current) return
+            yield* bus.publish(VcsEvent.BranchUpdated, { branch: next.branch.current })
+          }).pipe(Effect.withSpan("Vcs.refreshBranch", { attributes: { file: event.data.file } })),
+        ),
+        Effect.forkScoped({ startImmediately: true }),
+      )
+    }
+
+    const info = Effect.fnUntraced(function* () {
+      if (!impl) return { branch: {} }
+      if (!cache) return yield* impl.info()
+      const current = yield* Ref.get(cache)
+      if (current.branch.default !== undefined) return current
+      // An unborn repository can gain its first default branch without changing HEAD.
+      const next = yield* impl.info()
+      yield* Ref.set(cache, next)
+      return next
+    })
+
     return Service.of({
       info: Effect.fn("Vcs.info")(function* () {
-        if (!impl) return { branch: {} }
-        return yield* impl.info()
+        return yield* info()
       }),
       status: Effect.fn("Vcs.status")(function* () {
         if (!impl) return []
@@ -60,5 +97,5 @@ const layer = Layer.effect(
 export const node = makeLocationNode({
   service: Service,
   layer: layer,
-  deps: [AppProcess.node, FSUtil.node, Location.node],
+  deps: [AppProcess.node, FSUtil.node, Location.node, Bus.node],
 })

packages/core/test/vcs.test.ts

@@ -2,18 +2,21 @@ import { $ } from "bun"
 import { describe, expect } from "bun:test"
 import fs from "fs/promises"
 import path from "path"
-import { Effect, Layer } from "effect"
+import { Effect, Fiber, Layer, Stream } from "effect"
 import { LayerNode } from "@opencode-ai/util/effect/layer-node"
+import { Bus } from "@opencode-ai/core/bus"
 import { Location } from "@opencode-ai/core/location"
 import { AbsolutePath } from "@opencode-ai/core/schema"
 import { Vcs } from "@opencode-ai/core/vcs"
+import { FileSystem } from "@opencode-ai/schema/filesystem"
+import { VcsEvent } from "@opencode-ai/schema/vcs-event"
 import { location } from "./fixture/location"
 import { tmpdir } from "./fixture/tmpdir"
 import { it } from "./lib/effect"
 
 const provide = (directory: string, input: { git?: boolean } = {}) =>
   Effect.provide(
-    LayerNode.compile(Vcs.node, [
+    LayerNode.compile(LayerNode.group([Vcs.node, Bus.node]), [
       [
         Location.node,
         Layer.succeed(
@@ -35,6 +38,13 @@ const withTmp = <A, E, R>(f: (directory: string) => Effect.Effect<A, E, R>) =>
     (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
   ).pipe(Effect.flatMap((tmp) => f(tmp.path)))
 
+const withGit = <A, E, R>(f: (directory: string) => Effect.Effect<A, E, R>) =>
+  withTmp((directory) =>
+    Effect.promise(() => initRepo(directory)).pipe(
+      Effect.andThen(f(directory).pipe(provide(directory, { git: true }))),
+    ),
+  )
+
 async function initRepo(directory: string) {
   await $`git init -b main`.cwd(directory).quiet()
   await $`git config core.fsmonitor false`.cwd(directory).quiet()
@@ -62,10 +72,9 @@ describe("Vcs", () => {
   )
 
   it.live("reports modified, deleted, and untracked files", () =>
-    withTmp((directory) =>
+    withGit((directory) =>
       Effect.gen(function* () {
         yield* Effect.promise(async () => {
-          await initRepo(directory)
           await fs.writeFile(path.join(directory, "keep.txt"), "one\ntwo\n")
           await fs.writeFile(path.join(directory, "gone.txt"), "bye\n")
           await commitAll(directory, "initial")
@@ -80,15 +89,45 @@ describe("Vcs", () => {
           { file: "keep.txt", additions: 1, deletions: 1, status: "modified" },
           { file: "new.txt", additions: 2, deletions: 0, status: "added" },
         ])
-      }).pipe(provide(directory, { git: true })),
+      }),
+    ),
+  )
+
+  it.live("caches branch info and publishes HEAD changes", () =>
+    withGit((directory) =>
+      Effect.gen(function* () {
+        yield* Effect.promise(async () => {
+          await fs.writeFile(path.join(directory, "file.txt"), "one\n")
+          await commitAll(directory, "initial")
+        })
+        const vcs = yield* Vcs.Service
+        const bus = yield* Bus.Service
+        expect(yield* vcs.info()).toEqual({ branch: { current: "main", default: "main" } })
+
+        const updated = yield* bus.subscribe(VcsEvent.BranchUpdated).pipe(
+          Stream.take(1),
+          Stream.runHead,
+          Effect.forkScoped({ startImmediately: true }),
+        )
+        yield* Effect.promise(() => $`git checkout -q -b feature`.cwd(directory).quiet())
+
+        yield* bus.publish(FileSystem.Event.Changed, { file: path.join(directory, "HEAD"), event: "change" })
+        expect(yield* vcs.info()).toEqual({ branch: { current: "main", default: "main" } })
+
+        yield* bus.publish(FileSystem.Event.Changed, { file: path.join(directory, ".git", "HEAD"), event: "change" })
+        expect(yield* Fiber.join(updated)).toMatchObject({
+          _tag: "Some",
+          value: { location: { directory }, data: { branch: "feature" } },
+        })
+        expect(yield* vcs.info()).toEqual({ branch: { current: "feature", default: "main" } })
+      }),
     ),
   )
 
   it.live("diffs the working copy against HEAD with patches", () =>
-    withTmp((directory) =>
+    withGit((directory) =>
       Effect.gen(function* () {
         yield* Effect.promise(async () => {
-          await initRepo(directory)
           await fs.writeFile(path.join(directory, "keep.txt"), "one\ntwo\n")
           await commitAll(directory, "initial")
           await fs.writeFile(path.join(directory, "keep.txt"), "one\nthree\n")
@@ -106,16 +145,15 @@ describe("Vcs", () => {
         expect(diff[0].deletions).toBe(1)
         expect(diff[1].patch).toContain("+hello")
         expect(diff[1].additions).toBe(1)
-      }).pipe(provide(directory, { git: true })),
+      }),
     ),
   )
 
   it.live("respects the context option", () =>
-    withTmp((directory) =>
+    withGit((directory) =>
       Effect.gen(function* () {
         const body = Array.from({ length: 20 }, (_, index) => `line-${index}`).join("\n") + "\n"
         yield* Effect.promise(async () => {
-          await initRepo(directory)
           await fs.writeFile(path.join(directory, "file.txt"), body)
           await commitAll(directory, "initial")
           await fs.writeFile(path.join(directory, "file.txt"), body.replace("line-10", "changed"))
@@ -127,15 +165,14 @@ describe("Vcs", () => {
         const tight = yield* vcs.diff("working", { context: 1 })
         expect(tight[0].patch).toContain("line-9")
         expect(tight[0].patch).not.toContain("line-0")
-      }).pipe(provide(directory, { git: true })),
+      }),
     ),
   )
 
   it.live("diffs before the first commit", () =>
-    withTmp((directory) =>
+    withGit((directory) =>
       Effect.gen(function* () {
         yield* Effect.promise(async () => {
-          await initRepo(directory)
           await fs.writeFile(path.join(directory, "new.txt"), "hello\n")
         })
         const vcs = yield* Vcs.Service
@@ -143,15 +180,14 @@ describe("Vcs", () => {
         const diff = yield* vcs.diff("working")
         expect(diff).toHaveLength(1)
         expect(diff[0].patch).toContain("+hello")
-      }).pipe(provide(directory, { git: true })),
+      }),
     ),
   )
 
   it.live("diffs a feature branch against the default branch", () =>
-    withTmp((directory) =>
+    withGit((directory) =>
       Effect.gen(function* () {
         yield* Effect.promise(async () => {
-          await initRepo(directory)
           await fs.writeFile(path.join(directory, "file.txt"), "one\n")
           await commitAll(directory, "initial")
         })
@@ -164,12 +200,11 @@ describe("Vcs", () => {
           await commitAll(directory, "feature change")
         })
         const diff = yield* vcs.diff("branch")
-        expect(yield* vcs.info()).toEqual({ branch: { current: "feature", default: "main" } })
         expect(diff.map((item) => ({ file: item.file, status: item.status }))).toEqual([
           { file: "file.txt", status: "modified" },
         ])
         expect(diff[0].patch).toContain("+two")
-      }).pipe(provide(directory, { git: true })),
+      }),
     ),
   )
 })