fix(reference): read linked worktree commit provenance (#677)

Signed-off-by: RudyCelekli <47457359+rudycelekli@users.noreply.github.com>

src/application/ReferenceSourceVcsAdapter.ts

@@ -1,6 +1,6 @@
 import fs from "node:fs";
-import { lstat } from "node:fs/promises";
-import { join } from "node:path";
+import { lstat, readFile } from "node:fs/promises";
+import { join, resolve } from "node:path";
 
 import { resolveRef } from "isomorphic-git";
 
@@ -31,7 +31,7 @@ export const readReferenceSourceVcs = async (
       : { kind: "unknown", head: null, dirty: null };
   }
   try {
-    const head = await resolveRef({ fs, dir: root, ref: "HEAD" });
+    const head = await resolveSourceHead(root);
     if (isAborted(signal)) return { kind: "unknown", head: null, dirty: null };
     return { kind: "git", head, dirty: null };
   } catch (cause: unknown) {
@@ -41,6 +41,42 @@ export const readReferenceSourceVcs = async (
   }
 };
 
+const resolveSourceHead = async (root: string): Promise<string> => {
+  const dotgit = join(root, ".git");
+  if (!(await lstat(dotgit)).isFile())
+    return resolveRef({ fs, dir: root, ref: "HEAD" });
+  const pointer = (await readFile(dotgit, "utf8")).replace(/\r?\n$/u, "");
+  if (!pointer.startsWith("gitdir: ") || pointer.length === 8)
+    throw new Error("Invalid Git directory pointer");
+  const gitdir = resolve(root, pointer.slice(8));
+  let commonDirectory: string;
+  try {
+    commonDirectory = resolve(
+      gitdir,
+      (await readFile(join(gitdir, "commondir"), "utf8")).replace(
+        /\r?\n$/u,
+        "",
+      ),
+    );
+  } catch (cause: unknown) {
+    if (errorCode(cause) !== "ENOENT") throw cause;
+    return resolveRef({ fs, dir: root, gitdir, ref: "HEAD" });
+  }
+  const head = (await readFile(join(gitdir, "HEAD"), "utf8")).trim();
+  if (!head.startsWith("ref: "))
+    return resolveRef({ fs, dir: root, gitdir, ref: "HEAD" });
+  const ref = head.slice(5);
+  const privateRef = ["refs/bisect/", "refs/rewritten/", "refs/worktree/"].some(
+    (prefix) => ref.startsWith(prefix),
+  );
+  return resolveRef({
+    fs,
+    dir: root,
+    gitdir: privateRef ? gitdir : commonDirectory,
+    ref,
+  });
+};
+
 const errorCode = (cause: unknown): string | undefined =>
   typeof cause === "object" && cause !== null && "code" in cause
     ? String(cause.code)

tests/boundary/filesystem/referenceSourceVcs.test.ts

@@ -0,0 +1,94 @@
+import { mkdir, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import { expect, it } from "vitest";
+import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
+import { execFileOutput } from "../../../src/process/ExecFileOutput.js";
+import { readReferenceSourceVcs } from "../../../src/application/ReferenceSourceVcsAdapter.js";
+
+it("reads a linked worktree's own branch and detached HEAD through shared Git refs", async () => {
+  const root = await createTestTempDirectory("rea-reference-worktree-");
+  const repository = join(root, "repository");
+  await mkdir(repository);
+  const git = (...args: string[]) =>
+    execFileOutput("git", args, { cwd: repository });
+  await git("init", "--initial-branch=main");
+  const commit = () =>
+    git(
+      "-c",
+      "user.name=REA fixture",
+      "-c",
+      "user.email=fixture@example.invalid",
+      "-c",
+      "commit.gpgsign=false",
+      "commit",
+      "--allow-empty",
+      "-m",
+      "fixture",
+    );
+  await commit();
+  const mainHead = (await git("rev-parse", "HEAD")).stdout.trim();
+  const linked = join(root, "linked");
+  await git("worktree", "add", "-b", "linked", linked);
+  await execFileOutput(
+    "git",
+    [
+      "-c",
+      "user.name=REA fixture",
+      "-c",
+      "user.email=fixture@example.invalid",
+      "-c",
+      "commit.gpgsign=false",
+      "commit",
+      "--allow-empty",
+      "-m",
+      "linked fixture",
+    ],
+    { cwd: linked },
+  );
+  const linkedHead = (
+    await execFileOutput("git", ["rev-parse", "HEAD"], { cwd: linked })
+  ).stdout.trim();
+  expect(linkedHead).not.toBe(mainHead);
+  expect(await readReferenceSourceVcs(repository)).toEqual({
+    kind: "git",
+    head: mainHead,
+    dirty: null,
+  });
+  expect(await readReferenceSourceVcs(linked)).toEqual({
+    kind: "git",
+    head: linkedHead,
+    dirty: null,
+  });
+  await git("pack-refs", "--all", "--prune");
+  expect(await readReferenceSourceVcs(linked)).toEqual({
+    kind: "git",
+    head: linkedHead,
+    dirty: null,
+  });
+  await execFileOutput("git", ["checkout", "--detach", mainHead], {
+    cwd: linked,
+  });
+  expect(await readReferenceSourceVcs(linked)).toEqual({
+    kind: "git",
+    head: mainHead,
+    dirty: null,
+  });
+  const relativePointer = join(root, "relative");
+  await mkdir(relativePointer);
+  await writeFile(
+    join(relativePointer, ".git"),
+    "gitdir: ../repository/.git\r\n",
+  );
+  expect(await readReferenceSourceVcs(relativePointer)).toEqual({
+    kind: "git",
+    head: mainHead,
+    dirty: null,
+  });
+  const controller = new AbortController();
+  controller.abort();
+  expect(await readReferenceSourceVcs(linked, controller.signal)).toEqual({
+    kind: "unknown",
+    head: null,
+    dirty: null,
+  });
+});