fix(server): git failures are read in English when macOS git follows the system language

apps/server/src/vcs/VcsProcess.test.ts

@@ -149,6 +149,55 @@ describe("VcsProcess.run", () => {
       }),
   );
 
+  // Without LANG, macOS Git follows the system language, as in an app launched from Finder.
+  it.effect("reads Git failures in English when Git would follow the system language", () =>
+    Effect.gen(function* () {
+      let attempts = 0;
+      const service = yield* VcsProcess.make.pipe(
+        Effect.provideService(
+          ProcessRunner.ProcessRunner,
+          ProcessRunner.ProcessRunner.of({
+            run: (input) =>
+              Effect.sync(() => {
+                attempts += 1;
+                return {
+                  stdout: "",
+                  stderr:
+                    attempts % 2 === 0
+                      ? ""
+                      : input.env?.LANGUAGE === "C"
+                        ? "fatal: Unable to create '/private/repo/.git/index.lock': File exists.\n"
+                        : "致命錯誤: 無法建立「/private/repo/.git/index.lock」：File exists。\n",
+                  code: ChildProcessSpawner.ExitCode(attempts % 2 === 0 ? 0 : 128),
+                  timedOut: false,
+                  stdoutTruncated: false,
+                  stderrTruncated: false,
+                  stdoutInvalidUtf8: false,
+                  stderrInvalidUtf8: false,
+                };
+              }),
+          }),
+        ),
+      );
+
+      const capture = yield* service
+        .run({
+          ...baseInput,
+          operation: VcsProcess.CHECKPOINT_CAPTURE_OPERATION,
+          args: ["add", "--all"],
+        })
+        .pipe(Effect.exit, Effect.forkChild({ startImmediately: true }));
+      yield* TestClock.adjust("1 second");
+      expect(Exit.isSuccess(yield* Fiber.join(capture))).toBe(true);
+      expect(attempts).toBe(2);
+
+      attempts = 0;
+      const error = yield* Effect.flip(service.run(baseInput));
+      assert.instanceOf(error, VcsProcessExitError);
+      expect(error.detail).toBe(VcsProcess.GIT_INDEX_LOCKED_DETAIL);
+    }),
+  );
+
   it.effect.each([
     {
       stderr: "fatal: fsync error on '.git/objects/a5/tmp_obj_Pseg66': Operation not supported",

apps/server/src/vcs/VcsProcess.ts

@@ -210,6 +210,9 @@ export const make = Effect.gen(function* () {
         ...(input.stdin !== undefined ? { stdin: input.stdin } : {}),
         ...(input.onStdoutChunk !== undefined ? { onStdoutChunk: input.onStdoutChunk } : {}),
         env: {
+          // Failures are read by English patterns; without LANG, macOS Git follows the system language.
+          // LANGUAGE leaves LC_CTYPE, which hooks inherit, alone.
+          ...(input.command === "git" ? { LANGUAGE: "C" } : {}),
           ...input.env,
           ...explicitBareRepositoryEnv({ ...process.env, ...input.env }, hostPlatform),
         },