github: Serialize git worktree initialization

            await run('sudo', 'mount', '-t', 'tmpfs', 'tmpfs', 'nixpkgs')

          }

          // Create all worktrees in parallel.

          await Promise.all(

            commits.map(async ({ sha, path }) => {

          // Git worktree setup can race when multiple worktrees are created and

          // initialized at the same time against one repository. See #511286.

          // Keep the setup sequential so shared repo config updates cannot contend.

          for (const { sha, path } of commits) {

            await run('git', 'worktree', 'add', join('nixpkgs', path), sha, '--no-checkout')

            await run('git', '-C', join('nixpkgs', path), 'sparse-checkout', 'disable')

            await run('git', '-C', join('nixpkgs', path), 'checkout', '--progress')

            })

          )

          }

          // Apply pin bump to untrusted worktree

          if (pin_bump_sha) {