--init in serde-json checkout panics

[nagisa]

$ git clone 'https://github.com/serde-rs/json.git' && cd json
$ cargo fuzz --init
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /checkout/src/libcore/option.rs:323
stack backtrace:
   1:     0x5623cfbb8d89 - std::sys::imp::backtrace::tracing::imp::write::hbb14611794d3841b
                        at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:42
   2:     0x5623cfbbdf6e - std::panicking::default_hook::{{closure}}::h6ed906c7818ac88c
                        at /checkout/src/libstd/panicking.rs:351
   3:     0x5623cfbbdb74 - std::panicking::default_hook::h23eeafbf7c1c05c3
                        at /checkout/src/libstd/panicking.rs:367
   4:     0x5623cfbbe36b - std::panicking::rust_panic_with_hook::hd0067971b6d1240e
                        at /checkout/src/libstd/panicking.rs:545
   5:     0x5623cfbbe1f4 - std::panicking::begin_panic::h1fd1f10a3de8f902
                        at /checkout/src/libstd/panicking.rs:507
   6:     0x5623cfbbe169 - std::panicking::begin_panic_fmt::haa043917b5d6f21b
                        at /checkout/src/libstd/panicking.rs:491
   7:     0x5623cfbbe0f7 - rust_begin_unwind
                        at /checkout/src/libstd/panicking.rs:467
   8:     0x5623cfbe860d - core::panicking::panic_fmt::he9c7f335d160b59d
                        at /checkout/src/libcore/panicking.rs:69
   9:     0x5623cfbe8544 - core::panicking::panic::hb790668694ff6b20
                        at /checkout/src/libcore/panicking.rs:49
  10:     0x5623cf93bebc - <core::option::Option<T>>::unwrap::hbd802f172b858ee2
                        at /checkout/src/libcore/macros.rs:21
  11:     0x5623cf949cc8 - cargo_fuzz::init_fuzz::hca902791dd2a2f92
                        at /home/nagisa/Documents/rust/cargo-fuzz/src/main.rs:80
  12:     0x5623cf949334 - cargo_fuzz::main::hba96e14eae3eda3f
                        at /home/nagisa/Documents/rust/cargo-fuzz/src/main.rs:46
  13:     0x5623cfbc526a - __rust_maybe_catch_panic
                        at /checkout/src/libpanic_unwind/lib.rs:98
  14:     0x5623cfbbeb16 - std::rt::lang_start::hb7fc7ec87b663023
                        at /checkout/src/libstd/panicking.rs:429
                        at /checkout/src/libstd/panic.rs:361
                        at /checkout/src/libstd/rt.rs:57
  15:     0x5623cf94d502 - main
  16:     0x7ff37431d290 - __libc_start_main
  17:     0x5623cf93a949 - _start
  18:                0x0 - <unknown>

[nagisa]

(that’s because the actual json crate is in another subdirectory within the checkout)

[Manishearth]

We need to be able to make this take a --manifest-path argument. And give a better error message here.