如图：

Cloning into 'extern_gflags'...

error: RPC failed; curl 56 LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 54

fatal: The remote end hung up unexpectedly

fatal: early EOF

fatal: index-pack failed

Cloning into 'extern_gflags'...

error: RPC failed; curl 56 LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 60

fatal: The remote end hung up unexpectedly

fatal: early EOF

fatal: index-pack failed

Cloning into 'extern_eigen3'...

error: RPC failed; curl 56 LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 60

fatal: The remote end hung up unexpectedly

fatal: early EOF

fatal: index-pack failed

Cloning into 'extern_pybind'...

error: RPC failed; curl 56 LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 60

fatal: The remote end hung up unexpectedly

fatal: early EOF

fatal: index-pack failed