William Chargin f448960105
Forbid accessing the cache/ directory at runtime (#614)
Summary:
We plan to allow plugins to store permanent data in `$SC/data/` and
temporary, ephemeral, or intermediate data in `$SC/cache/`. The latter
subtree will be excluded from the static site at build time, so it
behooves us to also exclude it from the development environment.

Test Plan:
Run `yarn start`. Then,

```shell
$ root='localhost:8080/api/v1/data'
$ curl -sI "${root}/repositoryRegistry.json" | head -1
HTTP/1.1 200 OK
$ curl -sI "${root}/data/sourcecred/example-git/github/view.json" | head -1
HTTP/1.1 200 OK
$ curl -sI "${root}/cache" | head -1
HTTP/1.1 400 Bad Request
$ curl -sI "${root}/cache/" | head -1
HTTP/1.1 400 Bad Request
$ curl -sI "${root}/cache/foo" | head -1
HTTP/1.1 400 Bad Request
$ curl -sI "${root}/cache/foo/bar/baz" | head -1
HTTP/1.1 400 Bad Request
```

Also, check that the app still works.

wchargin-branch: exclude-cache-from-dev-server
2018-08-07 11:17:03 -07:00
..
2018-05-08 14:56:06 -07:00