fix(server): keep worktree creation working when git config is locked

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

@@ -2560,6 +2560,44 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
       }),
     );
 
+    it.effect("still creates the worktree when the base-ref config is locked", () =>
+      Effect.gen(function* () {
+        const cwd = yield* makeTmpDir();
+        const { initialBranch } = yield* initRepoWithCommit(cwd);
+        const pathService = yield* Path.Path;
+        const fileSystem = yield* FileSystem.FileSystem;
+        const worktreePath = pathService.join(yield* makeTmpDir("git-worktrees-"), "locked-config");
+        yield* writeTextFile(cwd, ".git/config.lock", "");
+        const driver = yield* GitVcsDriver.GitVcsDriver;
+
+        const created = yield* driver.createWorktree({
+          cwd,
+          path: worktreePath,
+          refName: initialBranch,
+          newRefName: "feature/locked-config",
+          baseRefName: initialBranch,
+        });
+
+        assert.deepEqual(created.worktree, {
+          path: worktreePath,
+          refName: "feature/locked-config",
+        });
+        assert.equal(
+          yield* git(worktreePath, ["branch", "--show-current"]),
+          "feature/locked-config",
+        );
+        assert.equal(
+          yield* fileSystem.readFileString(pathService.join(worktreePath, "README.md")),
+          "# test\n",
+        );
+        assert.equal(
+          yield* driver.readConfigValue(worktreePath, "branch.feature/locked-config.gh-merge-base"),
+          null,
+        );
+        assert.equal(yield* fileSystem.exists(pathService.join(cwd, ".git/config.lock")), true);
+      }),
+    );
+
     it.effect("reports checkout progress during parallel worktree creation", () =>
       Effect.gen(function* () {
         const cwd = yield* makeTmpDir();

apps/server/src/vcs/GitVcsDriverCore.ts

@@ -3186,7 +3186,14 @@ export const makeGitVcsDriverCore = Effect.fn("makeGitVcsDriverCore")(function*
         "config",
         `branch.${input.newRefName}.gh-merge-base`,
         baseBranch,
-      ]);
+      ]).pipe(
+        Effect.catch((cause) =>
+          Effect.logWarning("worktree base-ref configuration failed; using base-branch fallback", {
+            worktreePath,
+            cause,
+          }),
+        ),
+      );
     }
 
     return {